Current concepts in instrumented knee-laxity testing

Passive Knee Stability After Anterior Cruciate Ligament Reconstruction Using the Endobutton or ToggleLoc With ZipLoop as a Femoral Fixation Device: A Comparison of 1654 Patients From the Danish Knee Ligament Reconstruction Registry

Background

Biomechanical studies show varying results regarding the elongation of adjustable fixation devices. This has led to growing concern over the stability of the ToggleLoc with ZipLoop used in anterior cruciate ligament (ACL) reconstruction (ACLR) in vivo.

Purpose/Hypothesis

The purpose of this study was to compare passive knee stability 1 year after ACLR in patients in whom the Endobutton or ToggleLoc with ZipLoop was used for femoral graft fixation. The hypothesis was that the ToggleLoc with ZipLoop would be inferior in knee stability to the Endobutton 1 year after primary ACLR.

Study Design

Cohort study; Level of evidence, 2.

Methods

Data from 3175 patients (Endobutton: n = 2807; ToggleLoc with ZipLoop: n = 368) were included from the Danish Knee Ligament Reconstruction Registry (DKRR) between June 2010 and September 2013. Data were retrieved from standardized ACL forms filled out by the operating surgeon preoperatively, during surgery, and at a clinical examination 1 year after surgery. Passive knee stability was evaluated using 1 of 2 arthrometers (Rolimeter or KT-1000 arthrometer) and the pivot-shift test. Using the same database, the number of reoperations performed up to 4 years after primary surgery was examined.

Results

Full data were available for 1654 patients (Endobutton: n = 1538; ToggleLoc with ZipLoop: n = 116). ACLR with both devices resulted in increased passive knee stability (P < .001). Patients who received the ToggleLoc with ZipLoop were found to have a better preoperative (P = .005 ) and postoperative (P < .001) pivot-shift test result. No statistically significant difference regarding the number of reoperations (P = .086) or the time to reoperation (P = .295) was found.

Conclusion

Patients who underwent fixation with the ToggleLoc with ZipLoop had improved passive knee stability 1 year after surgery, measured by anterior tibial translation and pivot-shift test results, similar to patients who underwent fixation with the Endobutton. No difference was seen in knee stability or reoperation rates between the 2 devices.

Self-reported functional recovery after reconstruction versus repair in acute anterior cruciate ligament rupture (ROTOR): a randomized controlled clinical trial

BACKGROUND

Anterior cruciate ligament (ACL) reconstruction is today's surgical gold standard for ACL rupture. Although it provides satisfactory results, not all patients return to their previous activity level and moreover, early posttraumatic osteoarthritis is not prevented. As such, a renewed interest has emerged in ACL suture repair combined with dynamic augmentation. Compared to ACL reconstruction, the hypothesized advantages of ACL suture repair are earlier return to sports, reduction of early posttraumatic osteoarthritis and preservation of the patient's native ACL tissue and proprioceptive envelope of the knee. In recent literature, ACL suture repair combined with dynamic augmentation tends to be at least equally effective compared to ACL reconstruction, but no randomized comparative study has yet been conducted.

METHODS/DESIGN

This study is a prospective, stratified, block randomized controlled trial. Forty-eight patients with an ACL rupture will be assigned to either a suture repair group with dynamic augmentation and microfracture of the femoral notch, or an ACL reconstruction group with autologous semitendinosis graft and all-inside technique. The primary objective is to investigate the hypothesis that suture repair of a ruptured ACL results in at least equal effectiveness compared with an ACL reconstruction in terms of patient self-reported outcomes (IKDC 2000 subjective scale) 1 year postoperatively. Secondary objectives are to evaluate patient self-reported outcomes (IKDC 2000, KOOS, Tegner, VAS), re-rupture rate, rehabilitation time required for return to daily and sports activities, achieved levels of sports activity, clinimetrics (Rolimeter, LSI, Isoforce) and development of osteoarthritis, at short term (6 weeks, 3, 6 and 9 months and 1 year), midterm (2 and 5 years) and long term (10 years) postoperatively.

DISCUSSION

A renewed interest has emerged in ACL suture repair combined with dynamic augmentation in the treatment of ACL rupture. Recent cohort studies show good short- and midterm results for this technique. This randomized controlled trial has been designed to compare the outcome of suture repair of a ruptured ACL, combined with DIS as well as microfracture of the femoral notch, with ACL reconstruction using autologous semitendinosus.

TRIAL REGISTRATION

Clinical Trials Register NCT02310854 (retrospectively registered on December 1st, 2014).

Prospective comparative study of knee laxity with four different methods in anterior cruciate ligament tears

BACKGROUND AND PURPOSE

Anterior knee laxity can be evaluated using different devices, the most commonly used being the Telos®, KT1000®, Rolimeter®, and GNRB®. However, the laxity values obtained with these devices have never been compared to one another. As such, the outcomes of studies using these different knee laxity measurement devices may not be comparable. The primary purpose of this study was to determine the side-to-side laxity difference in patients with one ACL-injured knee, using each of these devices, and to compare the values obtained from each. We hypothesized that the measurements of laxity would vary depending on the device used.

METHODS

This was a prospective study. All patients with an ACL injury, in which surgical reconstruction was planned, underwent pre-operative knee laxity measurements using four different devices. The concordance correlation coefficient (CCC) of the results was compared between the four devices.

RESULTS

The study enrolled 52 patients. With regard to the values of the side-to-side differences, the KT1000® and the GNRB® obtained the most similar values (CCC = 0.51, 95% CI 0.37-0.63). The two devices with the lowest correlation were the Telos® and the Rolimeter® (CCC = 0.04, 95% CI - 0.14-0.23). The comparability was considered average for the KT1000® and GNRB® and poor for the other devices.

CONCLUSIONS

The knee laxity devices used in regular practice are not comparable to one another. As a result, caution must be taken when comparing results from studies using these different devices.

Evaluation of reproducibility of robotic knee testing device (GNRB) on 60 healthy knees

Introduction

There is a main concern about the usefulness and the accuracy of the different laximeters. The GnrB device is becoming more popular, but according to the literature it's not clear whether it is fully reliable.

Objective

GNRB laxity measurements are not reproducible for measurement of anterior translation of the tibia.

Material and methods

We analyzed the reproducibility of GNRB measurements in healthy subjects by the Test-Retest method in 2 sessions.

Results

30 pairs of healthy knees were assessed. Test-Retest agreement was poor for both absolute values and for differentials at 134 and 200 N with an intra-class correlation ranging from 0.210 to 0.486. There was a significant differance in anterior tibial translation, in side-to-side difference, according to the patellar pressure.

Conclusion

The reproducibility is found to be poor under optimum conditions of comparability. The patellar pressure influences strongly thelaxity value.

Validation of a computational knee joint model using an alignment method for the knee laxity test and computed tomography

BACKGROUND

Computational models have been identified as efficient techniques in the clinical decision-making process. However, computational model was validated using published data in most previous studies, and the kinematic validation of such models still remains a challenge. Recently, studies using medical imaging have provided a more accurate visualization of knee joint kinematics.

OBJECTIVE

The purpose of the present study was to perform kinematic validation for the subject-specific computational knee joint model by comparison with subject's medical imaging under identical laxity condition.

METHODS

The laxity test was applied to the anterior-posterior drawer under 90° flexion and the varus-valgus under 20° flexion with a series of stress radiographs, a Telos device, and computed tomography. The loading condition in the computational subject-specific knee joint model was identical to the laxity test condition in the medical image.

RESULTS

Our computational model showed knee laxity kinematic trends that were consistent with the computed tomography images, except for negligible differences because of the indirect application of the subject's in vivo material properties.

CONCLUSIONS

Medical imaging based on computed tomography with the laxity test allowed us to measure not only the precise translation but also the rotation of the knee joint. This methodology will be beneficial in the validation of laxity tests for subject- or patient-specific computational models.

THE DIAGNOSTIC ACCURACY OF THE LEVER SIGN FOR DETECTING ANTERIOR CRUCIATE LIGAMENT INJURY

Background

An alternative physical examination procedure for evaluating the integrity of the anterior cruciate ligament (ACL) has been proposed in the literature but has not been validated in a broad population of patients with a symptomatic complaint of knee pain for its diagnostic value.

Purpose

To investigate the diagnostic accuracy of the Lever Sign to detect ACL tears and compare the results to Lachman testing in both supine and prone positions.

Study design

Prospective, blinded, diagnostic accuracy study.

Methods

Sixty-two consecutive patients with a complaint of knee pain were independently evaluated for the status of the ACL's integrity with the Lever Sign and the Lachman test in a prone and supine by a blinded examiner before any other diagnostic assessments were completed.

Results

Twenty-four of the 60 patients included in the analysis had a torn ACL resulting in a prevalence of 40%. The sensitivity of the Lever Sign, prone, and supine Lachman tests were 38, 83, and 67 % respectively and the specificity was 72, 89, and 97% resulting in positive likelihood ratios of 1.4, 7.5, and 24 and negative likelihood ratios of 0.86, 0.19, and 0.34 respectively. The positive predictive values were 47, 83, and 94% and the negative predictive values were 63, 89, and 81% respectively. The diagnostic odds ratios were 1.6, 40, and 70 with a number needed to diagnose of 10.3, 1.4, and 1.6 respectively.

Conclusions

The results of this study suggest that Lever Sign, in isolation, does not accurately detect the status of the ACL. During the clinical examination, the Lever Sign should be used as an adjunct to the gold standard assessment technique of anterior tibial translation assessment as employed in the Lachman tests in either prone or supine position.

Level of Evidence

2.

Test-retest reliability of repeated knee laxity measurements in the acute phase following a knee trauma using a Rolimeter

The purpose was to examine the test-retest reliability of the Rolimeter measurement procedure in the acute time phase, following a substantial knee trauma. In total, 15 participants with acute knee trauma were examined by one single observer at three different time-points with the Rolimeter using a maximum force. The selected time-points were: baseline (0–7 days after the trauma), midpoint (3–4 weeks after the trauma), and endpoint (3–4 weeks after the trauma). The anterior-posterior displacement was recorded where the endpoint evaluation was used as the reference value. The mean anterior laxity scores remained constant over the measurement time-points for both knees, with an anterior laxity that was 2.7 mm higher (on average) in the injured than the noninjured knee (9.5 mm vs. 6.8 mm). The mean difference (i.e., bias) between laxity scores, for the injured knee, measured at endpoint versus baseline was 0.2±1.0 mm and −0.2±1.1 mm when measured at endpoint versus midpoint, with average typical errors of 0.7 and 0.8 mm and intra-class correlations that were very strong (both r=~0.93). For the same comparisons on the noninjured knee, systematic bias was close to zero (0.1±0.3 and −0.1±0.3 mm, respectively), and both the intra-class correlations were almost perfect (r=~0.99). The current study implicates that repeated Rolimeter measurements are relatively reliable for quantifying anterior knee laxity during the acute time-phases following knee trauma. Hence, the Rolimeter, in combination with manual tests, seems to be a valuable tool for identifying anterior cruciate ligament injuries.

Global rotation has high sensitivity in ACL lesions within stress MRI

PURPOSE

This study aims to objectively compare side-to-side differences of P-A laxity alone and coupled with rotatory laxity within magnetic resonance imaging, in patients with total anterior cruciate ligament (ACL) rupture.

METHODS

This prospective study enrolled sixty-one patients with signs and symptoms of unilateral total anterior cruciate ligament rupture, which were referred to magnetic resonance evaluation with simultaneous instrumented laxity measurements. Sixteen of those patients were randomly selected to also have the contralateral healthy knee laxity profile tested. Images were acquired for the medial and lateral tibial plateaus without pressure, with postero-anterior translation, and postero-anterior translation coupled with maximum internal and external rotation, respectively.

RESULTS

All parameters measured were significantly different between healthy and injured knees (P < 0.05), with exception of lateral plateau without stress. The difference between injured and healthy knees for medial and lateral tibial plateaus anterior displacement (P < 0.05) and rotation (P < 0.001) was statistically significant. It was found a significant correlation between the global rotation of the lateral tibial plateau (lateral plateau with internal + external rotation) with pivot-shift, and between the anterior global translation of both tibial plateaus (medial + lateral tibial plateau) with Lachman. The anterior global translation of both tibial plateaus was the most specific test with a cut-off point of 11.1 mm (93.8 %), and the global rotation of the lateral tibial plateau was the most sensitive test with a correspondent cut-off point of 15.1 mm (92.9 %).

CONCLUSION

Objective laxity quantification of ACL-injured knees showed increased sagittal laxity, and simultaneously in sagittal and transversal planes, when compared to their healthy contralateral knee. Moreover, when measuring instability from anterior cruciate ligament ruptures, the anterior global translation of both tibial plateaus and global rotation of the lateral tibial plateau add diagnostic specificity and sensitivity. This work strengthens the evidence that the anterior cruciate ligament plays an important biomechanical role in controlling the anterior translation, but also both internal and external rotation. The high sensitivity and specificity of this device in objectively identifying and measuring the multiplanar instability clearly guides stability restoration clinical procedures. Level of evidence Cross-sectional study, Level III.

Anatomic Reconstruction of the Anterior Cruciate Ligament of the Knee With or Without Reconstruction of the Anterolateral Ligament: A Randomized Clinical Trial

BACKGROUND

Rotational instability of the knee remains an issue after anterior cruciate ligament (ACL) reconstruction. Hypothesis/Purpose: The purpose was to evaluate the subjective and objective outcomes of combined reconstruction of the ACL and anterolateral ligament (ALL) of the knee. The hypothesis was that favorable outcomes can be achieved with this surgical procedure compared with isolated anatomic reconstruction of the ACL.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

One hundred ten patients with a unilateral ACL injury and high-grade pivot shift were randomly assigned to undergo either combined ACL and ALL reconstruction (group A) or isolated ACL reconstruction (group B). Preoperative and postoperative evaluations of the patients were conducted by obtaining history details, recording physical examination findings, measuring knee laxity using the KT-1000 arthrometer, and using validated outcome scores for the knee. P < .05 was considered as the cut-off level of statistical significance. The Fisher exact and Mann-Whitney U tests were used to assess statistical significance.

RESULTS

At a mean follow-up of 27 months, 53 and 50 patients in groups A and B, respectively, were available for analysis. No statistically different outcomes were found between the 2 groups except for the KT-1000 arthrometer values. The median KT-1000 arthrometer result for combined ACL and ALL reconstruction was 1.3 mm, while the median result for isolated ACL reconstruction was 1.8 mm ( P < .001). None of the patients (n = 0; 0.0%) who underwent combined ACL and ALL reconstruction had anterior translation of greater than 5 mm at maximum pulling strength compared with their normal knees at final follow-up. On the other hand, 3 (6.0%) patients who underwent isolated ACL reconstruction had anterior translation of more than 5 mm. No serious complications were found in both groups.

CONCLUSION

Combined ACL and ALL reconstruction was found to be effective in improving subjective and objective outcomes. Nevertheless, these findings were not significantly superior to isolated ACL reconstruction except for the instrumented knee laxity testing results. This might indicate that ALL reconstruction should not be performed routinely for patients undergoing ACL reconstruction.

Do ground reaction forces during unilateral and bilateral movements exhibit compensation strategies following ACL reconstruction?

PURPOSE

The aims of the study were (1) to evaluate the leg asymmetry assessed with ground reaction forces (GRFs) during unilateral and bilateral movements of different knee loads in anterior cruciate ligament (ACL) reconstructed patients and (2) to investigate differences in leg asymmetry depending on the International Knee Documentation Committee Subjective Form (IKDC) in order to identify potential compensation strategies.

METHODS

The knee function of 50 ACL reconstructed (patella tendon) patients was examined at 31 ± 7 months after the surgery. GRFs were quantified during the sit-to-stand and stand-to-sit test, the step-up and step-down test, and the two- and one-leg vertical jump. Further, the IKDC score, the anterior-posterior knee laxity, and the concentric torque of the quadriceps and hamstring muscles were evaluated.

RESULTS

Differences between the operated and non-operated leg were found in the knee laxity, the quadriceps torque, and GRFs. The patients with low IKDC scores demonstrated greater leg asymmetries in GRFs compared to the patients with high IKDC scores.

CONCLUSIONS

ACL reconstructed patients showed GRF asymmetries during unilateral and bilateral movements of different knee loads. Three compensation strategies were found in patients with low subjective knee function: (1) a reduced eccentric load, (2) an inter-limb compensation during bilateral movements, and (3) the avoidance of high vertical impact forces. These compensation strategies may be indicative of a protective adaptation to avoid excessive ACL strain. GRF measurements are practicable and efficient tools to identify individual compensation strategies during early rehabilitation.

Computational model-based probabilistic analysis of in vivo material properties for ligament stiffness using the laxity test and computed tomography

The objective of this paper was to evaluate in vivo material properties in order to address technical aspects of computational modeling of ligaments in the tibiofemoral joint using a probabilistic method. The laxity test was applied to the anterior-posterior drawer under 30° and 90° of flexion with a series of stress radiographs, a Telos device, and computed tomography. Ligament stiffness was investigated using sensitivity analysis based on the Monte-Carlo method with a subject-specific finite element model generated from in vivo computed tomography and magnetic resonance imaging data, subjected to laxity test conditions. The material properties of ligament stiffness and initial ligament strain in a subject-specific finite element model were optimized to minimize the differences between the movements of the tibia and femur in the finite element model and the computed tomography images in the laxity test. The posterior cruciate ligament was the most significant factor in flexion and posterior drawer, while the anterior cruciate ligament primarily was the most significant factor for the anterior drawer. The optimized material properties model predictions in simulation and the laxity test were more accurate than predictions based on the initial material properties in subject-specific computed tomography measurement. Thus, this study establishes a standard for future designs in allograft, xenograft, and artificial ligaments for anterior cruciate ligament and posterior cruciate ligament injuries.

Passive anterior tibial translation in women with and without joint hypermobility: an exploratory study

AIM

Generalized joint hypermobility (GJH) is a frequent entity, which is still not fully understood. Symptoms associated with GJH are musculoskeletal disorders, decreased balance, impaired proprioception and chronic pain. The purpose of this study was to compare the passive anterior tibial translation (TT) in terms of distance and corresponding force between normomobile (NM) and hypermobile (HM) as well as between NM, symptomatic (HM-s) and asymptomatic (HM-as) hypermobile women.

METHODS

A total of 195 women, 67 NM and 128 HM, whereof 56 were further classified as HM-s and 47 as HM-as, participated in this study. Passive TT was measured using an adapted Rolimeter. A manual traction force was applied and the distance of the translation measured. For the analysis, maximal translation (TTmax) and the respective force as well as the distance at 40N (TTF40) and 80N (TTF80) traction force were determined. The NM and HM groups were compared using independent samples t-tests, whereas the NM, HM-s and HM-as groups were compared using one-way analyses of variance with Tukey post hoc tests (significance level P ≤ 0.05).

RESULTS

Comparisons revealed higher values for the variables TTmax, TTF40 and TTF80 in the HM compared to the NM group. In addition, TTmax and TTF80 were found to be higher in the HM-s compared to the NM group.

CONCLUSIONS

HM women showed significantly higher TT distances, which were even more accentuated in those having symptoms. The findings point toward less passive stability of the knee joint and thus maybe a need of higher muscle activation in order to stabilize the joint.

Anterior cruciate ligament assessment using arthrometry and stress imaging

Arthrometry and stress imaging are useful clinical tools for the objective assessment of anterior cruciate ligament (ACL) integrity. They are most frequently used for the diagnosis of a complete ACL tear when other workup is equivocal, in conjunction with history and clinical exam findings. Other applications include the diagnosis of partial ACL tears, injury prognosis, and post-operative monitoring. However, further studies are needed to validate these uses. Many different devices and techniques exist for objective examination, which have been compared in recent literature. Reliability and validity measures of these methods vary, and often depend upon examiner familiarity and skill. The KT series of devices is the current gold standard for arthrometry, although the newer robotic GNRB device shows promising early results. Newer methods of data interpretation have been developed for stress imaging, and portable technology may impact this field further.

Combined Biplanar High Tibial Osteotomy, Anterior Cruciate Ligament Reconstruction, and Abrasion/Microfracture in Severe Medial Osteoarthritis of Unstable Varus Knees

PURPOSE

To determine survivorship and functional results of medial open-wedge high tibial osteotomy (HTO) combined with anterior cruciate ligament reconstruction (ACLR) and a chondral resurfacing (CR) procedure (abrasion/microfracture) in patients with Kellgren-Lawrence grade 3 and 4 osteoarthritis with full-thickness cartilage defects, anterior cruciate ligament (ACL) insufficiency, and varus malalignment.

METHODS

From October 2005 to March 2009, all combined HTO (fixation with angular stable internal fixator), ACLR, and CR procedures in knees with symptomatic medial osteoarthritis (Kellgren-Lawrence grade 3 and 4), ACL insufficiency, varus malalignment (>4°), and full-thickness large-area cartilage defects were prospectively surveyed with a minimum follow-up period of 5 years regarding survival (not requiring arthroplasty), functional outcome (subjective International Knee Documentation Committee [IKDC] score), and subjective satisfaction. Clinical evaluation (objective IKDC parameters and KT-1000 [MEDmetric, San Diego, CA] measurement), radiologic evaluation, and revision arthroscopy were performed between 1 and 2 years postoperatively.

RESULTS

Twenty-three knees (mean age, 47.0 ± 5.8 years) were included. The rate of follow-up was 100% at 6.0 ± 0.8 years (range, 5.2 to 7.5 years), with no arthroplasty until then. The mean subjective IKDC score improved from 47.7 ± 11.1 to 72.8 ± 15.0 at 1 year, 70.9 ± 16.0 at 3 years, and 73.1 ± 16.4 at 5 years (P < .001). Clinical examination and revision arthroscopy were performed in 22 cases (95.5%) at 1.3 ± 0.5 years (range, 1.0 to 2.0 years). Four ACL grafts (18.1%) were insufficient, and 2 grafts (9.1%) were stable but showed signs of degeneration. Good cartilage regeneration was seen in most cases, but no correlation with subjective IKDC score was apparent (P = .528).

CONCLUSIONS

HTO in combination with ACLR and a CR procedure is effective in the treatment of severe medial osteoarthritis with concomitant ACL insufficiency and varus malalignment. The effect of the CR, as well as the reason for the considerable rate of graft insufficiency, remains unclear.

Tibial rotation influences anterior knee stability--a robot-aided in-vitro study

BACKGROUND

Anterior cruciate ligament rupture can lead to symptomatic instability, especially during pivoting activities, which are often associated with increased anterior and rotational tibial loading. Therefore, the purpose of our robot-aided in-vitro study was to analyze the influence of tibial rotation on anterior knee stability under three anterior cruciate ligament conditions.

METHODS

Ten human knee specimens were examined using a robotic system. Anterior tibial translations were measured during anterior force application at internally and externally rotated positions of the tibia (5° steps until 4 Nm was reached) at 20°, 60°, and 90° of flexion. The native knee was compared with the knee with deficient and replaced anterior cruciate ligament.

FINDINGS

Tibial rotation significantly influenced anterior tibial translation (P<0.001), with differences of up to 12 mm between the largest and smallest anterior translation in the deficient knee. The largest influence of the anterior cruciate ligament on anterior translation was found in slightly externally rotated positions of the tibia (5°-10° at 20° of flexion; 0°-5° at 90° of flexion). Significantly increased anterior tibial translation (up to 7 mm) was measured after anterior cruciate ligament resection, which could be almost completely restored by the replacement (remaining difference<1mm) over a wide range of tibial rotations.

INTERPRETATION

Tibial rotation clearly influences anterior tibial translation. Because the greatest effect of the anterior cruciate ligament was found in slightly externally rotated positions of the tibia, increased attention to tibial rotation should be paid when performing the Lachman and anterior drawer tests.

Practicability for robot-aided measurement of knee stability in-vivo

Background

For the analysis of different treatments concerning anterior cruciate ligament (ACL) rupture, objective methods for the quantification of knee stability are needed. Therefore, a new method for in-vivo stability measurement using a robotic testing system should be developed and evaluated.

Methods

A new experimental setting was developed using a KUKA robot and a custom-made chair for the positioning and fixation of the participants. The tibia was connected to the robot via a Vacoped shoe and magnetic buttons, providing adequate safety. Anterior tibial translation and internal tibial rotation were measured on both legs of 40 healthy human subjects at 30°, 60° and 90° of flexion, applying anterior forces of 80 N and internal torques of 4 Nm, respectively.

Results

While the mean differences between the right and left leg measured for anterior tibial translation were within an acceptable range (<1.5 mm), the absolute values were substantially large (38–40.5 mm). For mean internal tibial rotation, between 17.5 and 20° were measured at the different sides and flexion angles, with a maximal difference of 0.75°. High reproducibility of the measurements could be demonstrated for both, anterior tibial translation (ICC(3,1) = 0.97) and internal tibial rotation (ICC(3,1) = 0.94).

Conclusions

Excellent results were achieved for internal tibial rotation, almost reproducing current in-vitro studies, but too large anterior tibial translation was measured due to soft-tissue compression. Therefore, high potential for the analysis of ACL related treatments concerning rotational stability is seen for the proposed method, but further optimization is necessary to enhance this method for the reliable measurement of anterior tibial translation.

Septic Arthritis After Arthroscopic Anterior Cruciate Ligament Reconstruction: Evaluation of an Arthroscopic Graft-Retaining Treatment Protocol

BACKGROUND

Septic arthritis after anterior cruciate ligament (ACL) reconstruction is a rare but severe complication. Treatment regimens differ, and optimal management has not been established.

PURPOSE

To determine the incidence of postoperative infections after ACL reconstruction, to identify the microbiological spectrum, and to evaluate a standardized graft-retaining treatment protocol consisting of sequential arthroscopic irrigation and debridement (I&D) procedures and antibiotic therapy until C-reactive protein levels are within normal range.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

From January 2004 to June 2014, a total of 7096 consecutive arthroscopic ACL reconstructions were performed at a single institution (5907 primary and 1189 revision reconstructions). Thirty-six cases with postoperative septic arthritis were identified and retrospectively analyzed with regard to incidence, clinical presentation, time to and number of arthroscopic reoperations, and microbiological findings. The follow-up examination consisted of a clinical examination, instrumeted measurement of laxity (KT-1000 arthrometer), classification according to objective and subjective International Knee Documentation Committee (IKDC) scores, and radiological evaluation.

RESULTS

The incidence of septic arthritis was 0.51% (n = 36), with 0.41% (n = 24) in primary and 1.01% (n = 12) in revision reconstructions (odds ratio, 2.5; P = .008). The first I&D was performed a mean (± SD) of 19.6 ± 10.6 days after the index procedure. Eradication was achieved in all patients after a mean of 2.25 ± 1.22 procedures, with graft retention in all but 1 patient (97.2%). The mean duration of antibiotic treatment was 5.4 ± 2.3 weeks (range, 2.1-12.9 weeks) and ≤ 4 weeks in 13 patients (36%). No recurrence of infections was seen. Coagulase-negative staphylococci (62.5%) and Staphylococcus aureus (21.9%) were the most frequent pathogens. Twenty-nine patients were available for follow-up (80.6%) after a mean 4.7 ± 3.2 years (range, 0.7-11.2 years). Two patients suffered recurrent nontraumatic ACL insufficiency (6.9%), and all others (93.1%) had an intact graft, with a mean KT-1000 arthrometer side-to-side difference of 1.4 ± 0.9 mm. The mean subjective IKDC score was 80.4 ± 11.2. No emergence or deterioration of osteoarthritis related to infections was seen.

CONCLUSION

Postoperative septic arthritis is rare but serious after arthroscopic ACL reconstruction. Graft retention and good to excellent clinical results can be obtained with an arthroscopic treatment protocol. The duration of antibiotic therapy should be based on the individual course.

Static and dynamic tibial translation before, 5 weeks after, and 5 years after anterior cruciate ligament reconstruction

PURPOSE

To evaluate static and dynamic tibial translation before, 5 weeks after, and 5 years after anterior cruciate ligament (ACL) reconstruction. To explore whether static and dynamic tibial translation are correlated.

METHODS

Ten patients undergoing quadruple hamstring tendon graft ACL reconstruction were evaluated before, 5 weeks after, and 5 years after ACL reconstruction. Sagittal tibial translation was measured during the Lachman test (static translation) and during gait (dynamic translation) using a CA-4000 electrogoniometer.

RESULTS

Five years after ACL reconstruction, static tibial translation did not differ between knees (Lachman test 90 N and 134 N n.s.). In contrast, there was greater maximal anterior tibial translation during gait in ACL-reconstructed knees than in uninjured knees (5.5 ± 1.4 vs. 4.5 ± 1.6 mm, P = 0.028). There were no differences in static or dynamic tibial translation between the 5-year follow-up and before ACL reconstruction or between the 5-year follow-up and the 5-week follow-up. There were no correlations between static and dynamic tibial translation.

CONCLUSION

Although static tibial translation did not differ between knees 5 years after ACL reconstruction, dynamic tibial translation during gait was greater in ACL-reconstructed knees than in uninjured knees. Neither static nor dynamic tibial translation changed 5 years after ACL reconstruction as compared to before surgery and 5 weeks after surgery. Static tibial translation did not correlate with dynamic tibial translation.

CLINICAL RELEVANCE

This study indicates that although the knee is stable during static measurements, kinematics during gait is impaired 5 years after ACL reconstruction. This may affect the return to sport and risk of osteoarthritis.

LEVEL OF EVIDENCE

Case series, Level IV.

Effects of Static Stretching and Playing Soccer on Knee Laxity

OBJECTIVE

This study investigated exercise-induced effects of static stretching and playing soccer on anterior tibial translation (ATT) of the knee joint.

DESIGN

Randomized controlled trial.

SETTING

University biomechanics laboratory.

PARTICIPANTS

Thirty-one athletes were randomly assigned into a stretching (26.9 ± 6.2 years, 1.77 ± 0.09 m, 67.9 ± 10.7 kg) and a control group (27.9 ± 7.4 years, 1.75 ± 0.08 m, 72.0 ± 14.9 kg). Thirty-one amateur soccer players in an additional soccer group (25.1 ± 5.6 years, 1.74 ± 0.10 m, 71.8 ± 14.8 kg). All participants had no history of knee injury requiring surgery and any previous knee ligament or cartilage injury.

INTERVENTIONS

The stretching group performed 4 different static stretching exercises with a duration of 2 × 20 seconds interspersed with breaks of 10 seconds. The soccer group completed a 90-minute soccer-specific training program. The control group did not perform any physical activity for approximately 30 minutes.

MAIN OUTCOME MEASURES

Anterior tibial translation was measured with the KT-1000 knee arthrometer at forces of 67 N, 89 N, and maximal manual force (Max) before and after the intervention.

RESULTS

There was a significant increase in ATT after static stretching and playing soccer at all applied forces. Maximal manual testing revealed a mean increase of ATT after static stretching of 2.1 ± 1.6 mm (P < 0.0005) and after playing soccer of 1.0 ± 1.5 mm (P = 0.001). The ATT increase after static stretching at 67 and 89 N is significantly higher than in controls. At maximum manual testing, significant differences were evident between all groups.

CONCLUSIONS

Static stretching and playing soccer increase ATT and may consequently influence mechanical factors of the anterior cruciate ligament. The ATT increase after static stretching was greater than after playing soccer.

CLINICAL RELEVANCE

The observed increase in ATT after static stretching and playing soccer may be associated with changes in kinesthetic perception and sensorimotor control, activation of muscles, joint stability, overall performance, and higher injury risk.

Rolimeter measurements are suitable as substitutes to stress radiographs in the evaluation of posterior knee laxity

PURPOSE

The quantification of posterior knee laxity is crucial in the evaluation of injuries to the posterior cruciate ligament (PCL) as it has important implications to the treatment for these injuries. The objective of this study was to compare the test results of stress radiography and instrumented drawer testing (Rolimeter) for the assessment of posterior knee laxity in patients with PCL injury.

METHODS

In 45 patients with an injury to the PCL, lateral radiographs of both knees were obtained under anterior and posterior tibial load (150 N) using a standardized approach. Patients with injury of the ACL to either knee were excluded from the study. During the same clinic visit, an instrumented measurement of anterior-posterior knee laxity was performed at 90° of knee flexion by an experienced examiner using the Rolimeter device. The mean side-to-side differences (SSD) of both (radiographic and instrumented) measurements were compared to each other, and the correlation was calculated using the Pearson coefficient.

RESULTS

The SSD (affected/healthy side) of posterior translation determined from the radiographs was 8.2 ± 3.2 mm, and the SSD of the instrumented measurement testing was 7.6 ± 3.2 mm. The mean difference between radiographic and Rolimeter test results was 1.8 ± 1.5 mm. The Pearson's correlation coefficient revealed a good correlation between both measurements of 0.74.

CONCLUSIONS

It may be suggested by the results of this study that under the absence of an ACL injury and a fixed posterior drawer sign, the Rolimeter is a suitable tool to assess the posterior laxity of the knee in the clinical setting. Its advantages are the absence of radiation to the patient, its availability, and the low cost. Therefore, the Rolimeter device may serve as a valuable alternative to stress radiography in the evaluation of PCL-injured patients.

LEVEL OF EVIDENCE

II.

Intratunnel versus extratunnel autologous hamstring double-bundle graft for anterior cruciate ligament reconstruction: a comparison of 2 femoral fixation procedures

BACKGROUND

Anatomic double-bundle anterior cruciate ligament (ACL) reconstruction provides excellent results for restoring normal kinematics to the knee. Nevertheless, strong evidence supporting an ideal method for fixation of the ACL graft is lacking.

HYPOTHESIS

Intratunnel femoral fixation of the ACL graft via a cross-pin fixation technique would provide better clinical and objective results than the extratunnel femoral fixation with cortical buttons.

STUDY DESIGN

Randomized clinical trial; Level of evidence, 2.

METHODS

Seventy patients with a unilateral ACL-deficient knee were randomly assigned to 1 of 2 femoral fixation groups. Group A (35 patients) was fixed with 2 bioabsorbable Rigidfix pins, 1 cross-pin per bundle, while group B (35 patients) was secured with 1 EndoButton cortical button per bundle. All femoral tunnels were created via an anteromedial portal, and a bioabsorbable Biointrafix interference screw was used for tibial fixation for both groups. The evaluation of the patients was performed by history details, clinical examination findings, measurement of the joint laxity by KT-1000 arthrometer, and use of validated patient outcome questionnaires. Statistical analysis was carried out with Fisher exact and Mann-Whitney U tests, with P<.05 considered the cutoff level of significance.

RESULTS

At a mean follow-up of 30 months, 34 and 32 patients of group A and B, respectively, were available for evaluation. There were no statistically significant differences between the treatment groups regarding the subjective and objective outcomes, except for KT-1000 arthrometer values. The median KT-1000 value of patients in the cross-pin fixation group was 1.30 mm, while the median value in the cortical button fixation group was 1.95 mm (P<.001). Four patients with ACL grafts that were fixed with cortical buttons demonstrated failure of stability via the instrumented knee laxity testing, while patients from the other group had no failures.

CONCLUSION

Intratunnel femoral fixation of the double-bundle ACL graft from the cross-pin fixation technique provided better instrumented knee laxity results than did the extratunnel femoral fixation with cortical buttons. Future larger studies comparing these 2 techniques should be conducted to ensure the availability of stronger evidence supporting the findings of this study.

Ultrasonographic test for complete anterior cruciate ligament injury

BACKGROUND

Although ultrasound (US) has a wide range of applications in orthopedic diagnostics, sonographic evaluation of traumatic anterior cruciate ligament (ACL) insufficiency is still inadequate. There is a growing need for diagnostic tests that allow for simple and reliable assessment of ACL instability. This investigation aims to evaluate feasibility of sonographic technique for diagnosing complete ACL insufficiency.

MATERIALS AND METHODS

Eighty three consecutive patients suspected of ACL injury were examined with sonographic, dynamic test of anterior instability. The translation of the intercondylar eminence against the patellar tendon was measured in the injured and opposite (injured) knee. Subsequent magnetic resonance imaging was performed on all patients. Forty-seven of them underwent a further arthroscopy. Five patients have been examined for the 2(nd) time to evaluate interclass and intraclass agreement and bias.

RESULTS

Complete ACL insufficiency has been confirmed in 37 patients. In those individuals, the total anterior knee translation and the difference between two joints (side-to-side difference) were significantly increased (8.67 mm standard deviation [SD] 2.65 mm in the affected knee versus 2.88 mm SD 1.26 mm in uninjured joint; P < 0.001). Based on a threshold of 2.0 mm for the side-to-side difference and 5.0 mm for the absolute translation, the sonographic test was found to have a sensitivity and specificity of 91.9% and 95.6%, respectively.

CONCLUSIONS

The present technique supports the clinician with additional fast and noninvasive diagnostic procedure that can facilitate the evaluation of anterior knee instability.

[Dorsal sagittal knee joint stability after endoprosthetic knee arthroplasty : Influence of preoperative joint stability and the type of implanted prosthesis]

BACKGROUND

Anterior knee pain is a known complication after implantation of a prosthesis and a possible reason is a posterior knee joint instability; however, the influence on postoperative stability is just as unknown as the possible influence of the type of prosthesis on postoperative stability.

AIM

This study investigated two possible preoperative and intraoperative influencing factors by determination of the preoperative joint stability and type of prosthesis.

Impact of Patient Sex on Clinical Outcomes: Data From an Anterior Cruciate Ligament Reconstruction Registry, 2008-2013

Background:

The Combined Quality Care Anterior Cruciate Ligament registry provides data for clinical research regarding primary anterior cruciate ligament (ACL) surgery.

Purpose:

To explore the data with regard to the clinical outcomes between sexes after ACL reconstruction in a Dutch population.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Data involving patients diagnosed with an ACL tear and eligible for surgery were recorded. Isokinetic muscle strength, functional muscle performance, and anterior-posterior translation of the knee joint were documented preoperatively and at 3, 6, 9, and 12 months postoperatively. Patients completed the Knee Injury and Osteoarthritis Outcome Score (KOOS), Lysholm, and Tegner rating scales during each examination using a web-based questionnaire.

Results:

Approximately 90% of ACL injuries occurred during sport activities. The mean (SD) age at surgery was 28 (11) years for both men and women, and the majority of patients were treated with hamstring tendon autografts (94%). Four percent received bone–patellar tendon–bone autografts, and 2% of the patients received other grafts. Preoperatively, the KOOS, Lysholm, and Tegner scores were significantly higher in males. Twelve months postoperatively, both sexes showed comparable isokinetic strength (P = .336), knee laxity (P = .680), and hop test for distance (P = .122) when comparing the injured with the uninjured side. Self-reported knee function was comparable between sexes as assessed by the KOOS (P = .202), Lysholm (P = .872), and Tegner (P = .767) questionnaires during the 12-month follow-up.

Conclusion:

One year after ACL surgery, all patients had improved greatly, showing only minor differences between sexes. The male group showed slightly better results when evaluating self-reported knee questionnaires. Comparable outcomes and knee function between sexes can therefore be presumed with patients who are treated with hamstring tendon autografts in a Dutch population.

Clinical Relevance:

These results can be used during the clinical evaluation of patients who are eligible for ACL reconstruction.

New sonographically-guided test for anterior knee instability - preliminary report

Aim of the study

Ultrasound examination is widely used in orthopedic diagnostics, however sonographic evaluation of traumatic anterior cruciate ligament insufficiency is still inadequate. Aim of this study is to evaluate diagnostic capability of a new sonographically-guided test for diagnosing complete anterior cruciate ligament insufficiency.

Material and methods

In 47 patients, with suspicion of unilateral anterior cruciate ligament injury (based on magnetic resonance imaging), the sonographically-guided test for anterior instability was performed. The translation of the intercondylar eminence against the patellar tendon was measured in both knees. Afterwards all patients underwent arthroscopy.

Results

In 37 patients, with arthroscopically confirmed complete anterior cruciate ligament insufficiency, the mean anterior knee translation was 8.3 mm (SD = 2.8) in affected knee vs. 3 mm (SD = 1.1) in uninjured knee (p < 0.001). In 10 patients with no anterior cruciate ligament insufficiency the difference between body sides was not significant (2.6 mm, SD = 1.4 in injured knee vs. 2.5 mm, SD = 1.1 in uninjured joint; p < 0.7753).

Conclusions

The proposed test supports the clinician with fast and non-invasive examination that can facilitate evaluation of anterior knee instability.

Technical note: a multi-dimensional description of knee laxity using radial basis functions

The net laxity of the knee is a product of individual ligament structures that provide constraint for multiple degrees of freedom (DOF). Clinical laxity assessments are commonly performed along a single axis of motion, and lack analyses of primary and coupled motions in terms of translations and rotations of the knee. Radial basis functions (RBFs) allow multiple DOF to be incorporated into a single method that accounts for all DOF equally. To evaluate this method, tibiofemoral kinematics were experimentally collected from a single cadaveric specimen during a manual laxity assessment. A radial basis function (RBF) analysis was used to approximate new points over a uniform grid space. The normalized root mean square errors of the approximated points were below 4% for all DOF. This method provides a unique approach to describing joint laxity that incorporates multiple DOF in a single model.

Validity of GNRB® arthrometer compared to Telos™ in the assessment of partial anterior cruciate ligament tears

PURPOSE

The main goal of this study was to compare the results of the GNRB(®) arthrometer to those of Telos™ in the diagnosis of partial thickness tears of the anterior cruciate ligament (ACL).

METHODS

A prospective study performed January-December 2011 included all patients presenting with a partial or full-thickness ACL tears without ACL reconstruction and with a healthy contralateral knee. Anterior laxity was measured in all patients by the Telos™ and GNRB(®) devices. This series included 139 patients, mean age 30.7 ± 9.3 years. Arthroscopic reconstruction was performed in 109 patients, 97 for complete tears and 12 single bundle reconstructions for partial thickness tears. Conservative treatment was proposed in 30 patients with a partial thickness tear. The correlation between the two devices was evaluated by the Spearman coefficient. The optimal laxity thresholds were determined with ROC curves, and the diagnostic value of the tests was assessed by the area under the curve (AUC).

RESULTS

The differential laxities of full and partial thickness tears were significantly different with the two tests. The correlation between the results of laxity measurement with the two devices was fair, with the strongest correlation between Telos™ 250 N and GNRB(®) 250 N (r = 0.46, p = 0.00001). Evaluation of the AUC showed that the informative value of all tests was fair with the best results with the GNRB(®) 250 N: AUC = 0.89 [95 % CI 0.83-0.94]. The optimal differential laxity threshold with the GNRB(®) 250 N was 2.5 mm (Se = 84 %, Sp = 81 %).

CONCLUSION

The diagnostic value of GNRB(®) was better than Telos™ for ACL partial thickness tears.

Influence of hip restriction on noncontact ACL rerupture

PURPOSE

This study investigated variables associated with hip restriction (reduced range of motion) in a group of soccer players presenting with noncontact rerupture of the anterior cruciate ligament (ACL) and compared results with a group of sport-matched healthy professional athletes.

METHODS

In this case series, 28 male soccer players with noncontact ACL rerupture were examined for clinical hip range of motion findings potentially associated with ACL rerupture, namely anterior knee displacement, internal-external hip rotation, and cruciate ligament insufficiency. Results were compared with data obtained from 27 healthy professional players. Patients presenting gross surgical errors (e.g. poorly positioned tunnel) or reporting major accidents affecting the lower limbs, such as leg or ankle fractures, were excluded from analysis. Internal-external rotation was measured in the supine position, with knee and hip at 90° of flexion. ACL insufficiency was assessed using the Pivot Shift test and the Lachman's test with the aid of a Rolimeter RM(®) arthrometer and confirmed by magnetic resonance imaging.

RESULTS

The most prevalent finding was a significantly lower mean internal-external hip rotation in the rerupture group (45.0°) when compared with healthy professional soccer players (56.2°).

CONCLUSION

Assessing hip restriction in patients presenting noncontact ACL rerupture showed to be extremely important during ACL reconstruction planning.

Methods to diagnose acute anterior cruciate ligament rupture: a meta-analysis of instrumented knee laxity tests

PURPOSE

The aims of this meta-analysis were to determine the sensitivity and specificity of the KT 1000 Arthrometer, Stryker Knee Laxity Tester and Genucom Knee Analysis System for ACL rupture. It was hypothesized that the KT 1000 test is the most sensitive and specific. Secondly, it was hypothesized that the sensitivity and specificity of the KT 1000 arthrometer increase when the amount of Newton force is increased.

METHODS

An electronic database search was performed using MEDLINE and EMBASE. All cross-sectional and cohort studies comparing one or more instrumented examination tests for diagnosing acute complete ACL rupture in living human subjects to an accepted reference standard such as arthroscopy, arthrotomy and MRI were included.

RESULTS

The sensitivity of the KT 1000 Arthrometer with 69 N was 0.54. With 89 N, the sensitivity was 0.78 and the specificity 0.92, and with maximum manual force, the sensitivity was 0.93 and the specificity 0.93. For the Stryker Knee Laxity Tester, the sensitivity was 0.82 and the specificity 0.90. And for the Genucom Knee Analysis System, the sensitivity was 0.74 and the specificity 0.82.

CONCLUSION

The KT Arthrometer performed with maximum manual force has the highest sensitivity, specificity, accuracy and positive predictive value for diagnosing ACL rupture.

LEVEL OF EVIDENCE

Meta-analysis, level I.

Combined ACL reconstruction and closing-wedge HTO for varus angulated ACL-deficient knees

PURPOSE

To report the medium-term clinical and radiographic outcomes of a group of patients who underwent anterior cruciate ligament (ACL) surgery combined with high tibial osteotomy (HTO) for varus-related early medial osteoarthritis (OA) and ACL deficiency knee.

METHODS

Thirty-two patients underwent single-bundle over-the-top ACL reconstruction or revision surgery and a concomitant closing-wedge lateral HTO. The mean age at surgery was 40.1 ± 8.1 years. Evaluation at a mean of 6.5 ± 2.7 years of follow-up consisted of subjective and objective IKDC, Tegner Activity Level, EQ-5D, VAS for pain and AP laxity assessment with KT-1000 arthrometer. Limb alignment and OA changes were evaluated on radiographs.

RESULTS

All scores significantly improved from pre-operative status to final follow-up. KT-1000 evaluation showed a mean side-to-side difference of 2.2 ± 1.0 mm. Two patients were considered as failures. The mean correction of the limb alignment was 5.6° ± 2.8°. Posterior tibial slope decreased at a mean of 1.2° ± 0.9°. At final follow-up, the mechanical axes crossed the medial-lateral length of tibial plateau at a mean of 56 ± 23 %, with only 1 patient (3 %) presenting severe varus alignment. OA progression was recorded only on the medial compartment (p = 0.0230), with severe medial OA in 22 % of the patients. No patients underwent osteotomy revision, ACL revision, UKA or TKA.

CONCLUSIONS

The described technique allowed patients with medial OA, varus alignment and chronic ACL deficiency to restore knee laxity, correct alignment and resume a recreational level of activity at 6.5 years of follow-up.

The diagnostic value of clinical tests, magnetic resonance imaging, and instrumented laxity in the differentiation of complete versus partial anterior cruciate ligament tears

PURPOSE

To evaluate the question of whether different arthroscopically confirmed anterior cruciate ligament (ACL) injury patterns have distinctive preoperative findings on clinical examination, instrumented laxity, and magnetic resonance imaging (MRI).

METHODS

Three hundred consecutive ACL-deficient patients with isolated ACL tears were evaluated with the Lachman test (LT), the pivot-shift test (PST), stress radiographs using the Telos Stress Device (Metax, Hungen, Germany), and MRI. After arthroscopic confirmation of the ACL injury, we grouped patients into 4 different ACL tear types (complete, partial anteromedial [AM] bundle intact, posterolateral [PL] bundle intact, and posterior cruciate ligament [PCL] healing), and partial tears were further evaluated for mechanical integrity and functionality of the remaining fibers.

RESULTS

PST grades of +2 and +3 were consistent with complete ACL tears (86%; P < .00001), whereas PST grades of 0 or +1 were strongly related to partial tears (76%; P < .00001). Instrumented laxity results showed a significant difference in side-to-side difference (SSD) of anterior tibial translation in complete tears (9.1 ± 3.4 mm) versus partial tears (5.2 ± 2.9 mm; P < .0001). Most PL-intact cases were "functional" (67%), with lower instrumented laxity values (SSD, 4.3 ± 2.3 mm) than the "nonfunctional" cases (SSD, 6.7 ± 2.9 mm; P < .001). The contrary was not observed for AM-intact cases (17% functional). Partial ACL tears with functional remaining fibers had PST grades of 0 or +1 and less than a 4 mm SSD in stress radiographs (sensitivity, 0.76; specificity, 0.90). Partial ACL tears with nonfunctional fibers had positive PST results and an SSD of anterior tibial displacement from 4 to 9 mm (sensitivity, 0.56; specificity, 0.92). Positive PST results and an SSD greater than 9 mm was recorded in complete ACL tears (sensitivity, 0.88; specificity, 0.96). MRI analysis revealed overlapping results between complete and partial tears.

CONCLUSIONS

Preoperative evaluation of different ACL tear types showed differences between complete and partial ACL tears with functional fibers in clinical examination and instrumented laxity tests. The combination of clinical tests and stress radiographs produced threshold values that distinguished complete from partial ACL tears, which may help the surgeon in the early identification of the presence of remaining functional fibers.

LEVEL OF EVIDENCE

Level III, case-control study.

Current concept in rotational laxity control and evaluation in ACL reconstruction

Rotation combined with translation; compose the three-dimensional motion of the knee subluxation in anterior cruciate ligament deficient knee. The worldwide scientists were focused initially on the translation part of this complex 3D motion, but since the beginning of the century there was a large interest on knee rotational laxity study. Lot of paper reported new devices and results with an explosion since the beginning of the decade. The purpose of this review is to provide an extensive critical analysis of the literature and clarify the knowledge on this topic. We will start with a dismemberment of different rotational laxities reported: the rotation coupled with translation in 2D tests such as Lachman test and anterior drawer test; the rotational envelope considering the maximum internal external rotation; and the "active rotation" occurring in 3D Pivot-shift (PS) test. Then we will analyze the knee kinematics and the role of different anterior cruciate ligament (ACL) bundle on rotation. A review of different mechanical and radiological devices used to assess the different rotations on ACL deficient knees will be presented. Two groups will be analyzed, dynamic and static conditions of tests. Navigation will be described precisely; it was the starter of this recent interest in rotation studies. Opto electronic and electromagnetic navigation systems will be presented and analyzed. We will conclude with the last generation of rotational laxity assessment devices, using accelerometers, which are very promising.

Objective evaluation of anterior knee laxity; comparison of the KT-1000 and GNRB® arthrometers

PURPOSE

Accurate measurement of laxity after anterior cruciate ligament (ACL) rupture is usually performed with the KT-1000 arthrometer, and reproducibility and reliability are discussed. A new arthrometer, the GNRB(®), has been recently developed in an attempt to improve intra- and inter-examiner reproducibility. The aim of this diagnostic study was to evaluate the intra- and inter-examiner reproducibility of the GNRB(®) and the KT-1000.

METHODS

Three protocols were designed to evaluate and compare the two arthrometers. Fifteen physiotherapists conducted tests on 15 subjects with healthy knees. The intra- and inter-reproducibility of the two tests were compared by analysis of variance and the F-test.

RESULTS

Measure reproducibility was significantly worst with the KT-1000 than with the GNRB(®) (machine effect, P < 0.001) regardless of operator experience. There was no significant difference between experienced and inexperienced examiners with the GNRB(®) (no 'examiners effect'). Regardless of the machine, there was a 'side effect' with healthy knees.

CONCLUSION

This clinical study demonstrates the superior intra- and inter-examiner reproducibility of the GNRB(®) over the KT-1000. There appears to be some technological advantages to using the GNRB(®) including pressure control of the patella, accuracy of the displacement transducer, control of the load on the calf, and control of hamstring activity.

LEVEL OF EVIDENCE

Diagnostic study, Level I.

A comparison of Telos™ stress radiography versus Rolimeter™ in the diagnosis of different patterns of anterior cruciate ligament tears

INTRODUCTION

Our knowledge on anterior cruciate ligament (ACL) pathomechanics has increased. The diagnosis of partial ACL tears must be accurate in order to adjust the operative planning to anatomic status and injury severity. Instrumented measurement of knee laxity is a useful preoperative tool to quantify anterior tibial translation and several laximetry tests are available. Yet, their accuracy remains to be established.

HYPOTHESIS

Clinical examination combined to instrumented laximetry with Telos™ 15 kg and/or Rolimeter™ would increase their sensitivity and specificity in the diagnosis of various ACL injury patterns.

MATERIALS AND METHODS

One hundred and seventy-seven patients were prospectively included. The ACL status was validated by arthroscopy. Around 69.5% had a complete ACL tear and 30.5% had a partial ACL tear.

RESULTS

Gross laxity with positive clinical tests was associated with complete ACL tears. Mean side-to-side difference was significantly greater with both laximetry methods in complete versus partial ACL tears. Laximetry results among different types of partial tears were not significantly different. Telos™ results were consistent with gross laxity confirmed by pivot-shift test, while this was not recorded with Rolimeter™. Gross laxity with clinical tests and anterior tibial translation more than 5mm with Telos™ were substantially associated with complete ACL tears.

DISCUSSION

The combination of standard clinical examination with Telos™ was more accurate than with Rolimeter™ in the preoperative identification of the ACL injury pattern. Applying additional diagnostic tools can help the surgeon to preoperatively diagnose partial or complete ACL ruptures and propose an injury-specific surgical treatment.

LEVEL OF EVIDENCE

Level III (case-control study).

Arthrometric curve-shape variables to assess anterior cruciate ligament deficiency

BACKGROUND

Instrumented measurement of asymmetry in anterior-posterior knee laxity is commonly used to assess anterior cruciate ligament integrity. Significant advances in arthrometric technology and data visualization have occurred since first generation arthrometers. However, little has changed with regard to diagnostic criteria employed. To our knowledge, no investigations have assessed the shape of laxity curves to diagnose anterior cruciate ligament (ACL) deficiency. We hypothesized that linear stiffness and compliance after positive curve inflection would be more sensitive and specific to anterior cruciate ligament injury than current measures and would require data from the involved limb only.

METHODS

Laxity curves were obtained from 130 knees on 65 subjects (Anterior Cruciate Injured n=15, Controls n=50) using a CompuKT Knee Ligament Arthrometer. Traditional diagnostic variables and novel descriptive curve-shape variables [(1) inflection point, (2) pre- and post-inflection linear stiffness and (3) a modified compliance index based on the post-inflection linear stiffness] were assessed for sensitivity to anterior cruciate ligament deficiency. Statistical interactions were evaluated using 2-by-2 ANOVA.

FINDINGS

Significant interactions (P<0.001) were identified for laxity symmetry, stiffness, compliance index and modified compliance index. Modified compliance index predicted anterior cruciate ligament deficiency with the highest sensitivity (93%) and specificity (100%). For a test performed on a single limb, modified compliance index demonstrated 98% sensitivity and 80% specificity.

INTERPRETATION

The modified compliance index is a highly sensitive and specific measure to diagnose anterior cruciate ligament deficiency, and may serve as a simple and accurate diagnostic tool for individuals without a healthy contralateral limb.

Assessment of rotatory laxity in anterior cruciate ligament-deficient knees using magnetic resonance imaging with Porto-knee testing device

PURPOSE

Objective evaluation of both antero-posterior translation and rotatory laxity of the knee remains a target to be accomplished. This is true for both preoperative planning and postoperative assessment of different ACL reconstruction emerging techniques. The ideal measurement tool should be simple, accurate and reproducible, while enabling to assess both ‘‘anatomy’’ and ‘‘function’’ during the same examination. The purpose of this study is to evaluate the clinical effectiveness of a new in-house developed testing device, the so-called Porto-knee testing device (PKTD). The PKTD is aimed to be used on the evaluation of both antero-posterior and rotatory laxity of the knee during MRI exams.

METHODS

Between 2008 and 2010, 33 patients with ACLdeficient knees were enrolled for the purpose of this study. All patients were evaluated in the office and under anesthesia with Lachman test, lateral pivot-shift test and anterior drawer test. All cases were studied preoperatively with KT-1000 and MRI with PKTD, and examinations performed by independent observers blinded for clinical evaluation. During MRI, we have used a PKTD that applies antero-posterior translation and permits free tibial rotation through a standardized pressure (46.7 kPa) in the proximal posterior region of the leg. Measurements were taken for both knees and comparing side-to-side. Five patients with partial ruptures were excluded from the group of 33.

RESULTS

For the 28 remaining patients, 3 women and 25 men, with mean age of 33.4 ± 9.4 years, 13 left and 15 right knees were tested. No significant correlation was noticed for Lachman test and PKTD results (n.s.). Pivot-shift had a strong positive correlation with the difference in anterior translation registered in lateral and medial tibia plateaus of injured knees (cor. coefficient = 0.80; p\0.05), and with the difference in this parameter as compared to side-to-side (cor. coefficient = 0.83; p\0.05). Considering the KT-1000 difference between injured and healthy knees, a very strong positive correlation was found for side-to-side difference in medial (cor. coefficient = 0.73; p\0.05) and lateral (cor. coefficient = 0.5; p\0.05) tibial plateau displacement using PKTD.

CONCLUSION

The PKTD proved to be a reliable tool in assessment of antero-posterior translation (comparing with KT-1000) and rotatory laxity (compared with lateral pivotshift under anesthesia) of the ACL-deficient knee during MRI examination.

LEVEL OF EVIDENCE

Therapeutic studies, Level IV.

Surgical technique: articulated external fixator for treatment of complex knee dislocation

BACKGROUND

Knee dislocation is a severe but relatively uncommon injury caused by violent trauma that can result in long-term complications, such as arthrofibrosis, stiffness, instability, and pain. Perhaps owing in part to its rarity, treatment of this injury is controversial. We therefore describe a treatment approach for these complex cases involving a novel dynamic knee external fixator.

DESCRIPTION OF TECHNIQUE

We performed open PCL reconstruction when possible and/or repair of other associated lesions. At the end of the surgical procedure, the surgeon applied an external fixator that reproduced normal knee kinematics, allowing early motion exercises and reducing the risk of joint stiffness while protecting the bony and soft tissue structures involved in the repair during the first healing phase.

PATIENTS AND METHODS

We retrospectively reviewed eight patients treated with this approach, four of whom had the PCL reconstructed and four of whom had only associated injuries reconstructed. We evaluated all patients with clinical scores (subjective International Knee Documentation Committee form, Lysholm score, and Tegner level), physical examination (objective International Knee Documentation Committee form), and KT-1000™ arthrometer for AP laxity. Minimum followup was 10 months (mean, 26 months; range, 10-45 months).

RESULTS

One patient had manipulation under anesthesia. The median Lysholm score was 76, Tegner level was 4, and subjective International Knee Documentation Committee was 73. All patients recovered to their preinjury work activity, except one unemployed patient. Stability was normal or nearly normal in five patients; the mean side-to-side difference in AP displacement with manual maximum force was 2.9 mm.

CONCLUSIONS

This approach with an external fixator allowed staged reconstruction and early motion and provided reasonable stability, ROM, and activity level at followup in patients with complex injuries.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Surgical technique: does mini-invasive medial collateral ligament and posterior oblique ligament repair restore knee stability in combined chronic medial and ACL injuries?

BACKGROUND

Residual laxity remains after ACL reconstruction in patients with combined chronic ACL and medial instability. The question arises whether to correct medial capsular and ligament injuries when Grade II and III medial laxity is present.

DESCRIPTION OF TECHNIQUE

We developed a mini-invasive medial ligament plasty to repair the medial collateral ligament to correct residual medial valgus and rotatory laxity after ACL reconstruction.

PATIENTS AND METHODS

We prospectively followed 36 patients with an ACL deficiency combined with chronic Grade II or III valgus and rotatory medial instability. The mean age was 37 years (range, 15-70 years). For all patients, we obtained preoperative and postoperative Knee Injury and Osteoarthritis Outcome, International Knee Documentation Committee, Lysholm, and Tegner Activity Level Scores. The minimum followup was 2 years (median, 3 years; range, 2-7 years).

RESULTS

The mean subjective International Knee Documentation Committee score improved from 36 preoperatively to 94 at the last followup. While all patients had an International Knee Documentation Committee score of Grade C or D preoperatively, no patient did postoperatively. The mean Knee Injury and Osteoarthritis Outcome Score improved from 45 preoperatively to 93 postoperatively. Valgus and external rotatory tests were negative in all patients. The mean Tegner activity level decreased from 7 preinjury to 6 postoperatively, and the mean Lysholm score improved from 40 preoperatively to 93 at last followup.

CONCLUSIONS

This simple technique restored medial stability and knee function to normal or nearly normal in all patients.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

The quality of bone surfaces may govern the use of model based fluoroscopy in the determination of joint laxity

The assessment of knee joint laxity is clinically important but its quantification remains elusive. Calibrated, low dosage fluoroscopy, combined with registered surfaces and controlled external loading may offer possible solutions for quantifying relative tibio-femoral motion without soft tissue artefact, even in native joints. The aim of this study was to determine the accuracy of registration using CT and MRI derived 3D bone models, as well as metallic implants, to 2D single-plane fluoroscopic datasets, to assess their suitability for examining knee joint laxity. Four cadaveric knees and one knee implant were positioned using a micromanipulator. After fluoroscopy, the accuracy of registering each surface to the 2D fluoroscopic images was determined by comparison against known translations from the micromanipulator measurements. Dynamic measurements were also performed to assess the relative tibio-femoral error. For CT and MRI derived 3D femur and tibia models during static testing, the in-plane error was 0.4 mm and 0.9 mm, and out-of-plane error 2.6 mm and 9.3 mm respectively. For metallic implants, the in-plane error was 0.2 mm and out-of-plane error 1.5 mm. The relative tibio-femoral error during dynamic measurements was 0.9 mm, 1.2 mm and 0.7 mm in-plane, and 3.9 mm, 10.4 mm and 2.5 mm out-of-plane for CT and MRI based models and metallic implants respectively. The rotational errors ranged from 0.5° to 1.9° for CT, 0.5-4.3° for MRI and 0.1-0.8° for metallic implants. The results of this study indicate that single-plane fluoroscopic analysis can provide accurate information in the investigation of knee joint laxity, but should be limited to static or quasi-static evaluations when assessing native bones, where possible. With this knowledge of registration accuracy, targeted approaches for the determination of tibio-femoral laxity could now determine objective in vivo measures for the identification of ligament reconstruction candidates as well as improve our understanding of the consequences of knee joint instability in TKA.

Anterior and posterior knee laxity in a young adult Korean population

PURPOSE

The purposes of this study were (1) to determine normal anterior and posterior knee laxity in a healthy young adult (20-30 years old) Korean population, (2) to compare knee laxity between the male and female populations, (3) to investigate whether generalized joint laxity affects anterior and posterior knee laxity, (4) to determine side-side differences between right and left knees, and thus, to determine normal values of side-side differences.

METHODS

Normal values of anterior and posterior knee laxity were measured in 100 healthy volunteers (50 men and 50 women) aged between 20 and 30 years. Stress radiography using a Telos device was performed in 20 and 70° of knee flexion for 134N anterior and posterior loads. Anterior and posterior tibial displacements relative to the femur condyle were measured using a computerized system.

RESULTS

In the 100 subjects (200 knees), anterior knee laxity was greater at 20° of flexion with a mean of 4.9 ± 2.3 mm (P < 0.05) and posterior knee laxity was greater at 70° of flexion with a mean of 4.6 ± 2.7 mm (P < 0.05). The mean side-side difference was 1.4 ± 0.9 mm (range, -3 to +3). Women had greater anterior laxity (P < 0.05) than men at both 20 and 70° of flexion, but posterior laxity was not different (ns). Generalized joint laxity was greater in women compared to men (P < 0.05). Subjects with generalized joint laxity had greater laxity than normal populations in both 20 and 70° of flexion (P < 0.05). Side-side differences between right and left knees were not significantly different in women and men or between subjects with normal and generalized joint laxity (ns).

CONCLUSIONS

This study suggests that the Korean population exhibits a wide range of normal anterior and posterior knee laxity, but small side-side differences. Subjects with generalized laxity showed greater knee laxity than those without, but side-side differences were less than 3 mm in all subjects. Thus, clinical guideline that a side-side difference more than 3 mm of anterior knee laxity is abnormal can be applicable for the subjects with generalized laxity.

Does chronic medial collateral ligament laxity influence the outcome of anterior cruciate ligament reconstruction?: a prospective evaluation with a minimum three-year follow-up

We have shown in a previous study that patients with combined lesions of the anterior cruciate (ACL) and medial collateral ligaments (MCL) had similar anteroposterior (AP) but greater valgus laxity at 30° after reconstruction of the ACL when compared with patients who had undergone reconstruction of an isolated ACL injury. The present study investigated the same cohort of patients after a minimum of three years to evaluate whether the residual valgus laxity led to a poorer clinical outcome. Each patient had undergone an arthroscopic double-bundle ACL reconstruction using a semitendinosus-gracilis graft. In the combined ACL/MCL injury group, the grade II medial collateral ligament injury was not treated. At follow-up, AP laxity was measured using a KT-2000 arthrometer, while valgus laxity was evaluated with Telos valgus stress radiographs and compared with the uninjured knee. We evaluated clinical outcome scores, muscle girth and time to return to activities for the two groups. Valgus stress radiographs showed statistically significant greater mean medial joint opening in the reconstructed compared with the uninjured knees (1.7 mm (SD 0.9) versus 0.9 mm (SD 0.7), respectively, p = 0.013), while no statistically significant difference was found between the AP laxity and the other clinical parameters. Our results show that the residual valgus laxity does not affect AP laxity significantly at a minimum follow up of three years, suggesting that no additional surgical procedure is needed for the medial collateral ligament in combined lesions.

Reliability and diagnostic accuracy of the Lachman test performed in a prone position

STUDY DESIGN

Prospective, blinded, diagnostic accuracy study.

OBJECTIVE

To investigate the reliability and diagnostic accuracy of the Lachman test, performed in a prone position, to detect the presence of an anterior cruciate ligament (ACL) tear. Direct arthroscopic visualization and a consensus of clinical findings, including joint arthrometry and magnetic resonance imaging, were used as the reference standards.

BACKGROUND

An alternative position for evaluating the integrity of the ACL has been proposed as a means for examiners with smaller hands to adequately stabilize the thigh of a larger individual; however, the diagnostic accuracy of this method has not been established.

METHODS

Fifty-two consecutive patients with a complaint of knee pain were independently evaluated in a prone position for the status of their ACL by 2 physical therapists, before any other diagnostic assessment. The 31 men and 21 women ranged in age from 16 to 57 (mean ± SD, 34.3 ± 4.2) years and in acuity of knee injury from 21 to 365 (mean ± SD, 195 ± 130) days.

RESULTS

Twenty-three of 52 (44%) of the patients had a torn ACL. The agreement between examiners was 90%, with a kappa coefficient of 0.81. The sensitivity of the prone Lachman test was 70% and the specificity was 97%, resulting in a positive likelihood ratio of 20.17 and a negative likelihood ratio of 0.32. The positive predictive value was 94% and the negative predictive value was 80%. The diagnostic odds ratio was 64.0, with a number needed to diagnose of 1.5.

CONCLUSION

The prone Lachman test is a reliable evaluation technique that can be used to confirm the presence of an ACL tear; however, the test should not be used as the sole criterion to rule out the presence of the injury.

LEVEL OF EVIDENCE

Diagnosis, level 2b.

Validation of a measurement device for instrumented quantification of anterior translation and rotational assessment of the knee

PURPOSE

A test setup for clinical use in the awake and non-anesthetized patient measuring anteroposterior translation and rotation of the knee joint is the subject of validation.

METHODS

A measuring device featuring fixation of the foot at 30° of knee flexion with varus/valgus stress posts for the knee was developed. Tibial rotation (external/internal) was imposed with a torque of 2 Nm on the footrest with the ankle locked in dorsiflexion. Anterior translation of the tibia in relation to the femur was measured with a commercially available arthrometer. Measurements were performed in a neutral position, internal rotation, and external rotation. Intrarater and inter-rater reliability was validated in 10 healthy volunteers (Cronbach α). We examined 10 patients with isolated anterior cruciate ligament (ACL) rupture, as well as 10 patients with ACL rupture plus medial instability and 10 patients with additional lateral instability. Side-to-side differences were used for calculation.

RESULTS

Comparison of healthy volunteers and subjects with isolated ACL rupture showed significant differences: internal rotation, 0.79 mm and 2.46 mm, respectively (P = .001); neutral position, 0.4 mm and 3.35 mm, respectively (P < .0001); and external rotation, 0.29 mm and 2.5 mm, respectively (P = .003). Significant differences (P = .008) were found between isolated ACL rupture and ACL rupture plus medial instability by use of the ratio of anterior translation in external rotation versus the neutral position. Inter-rater reliability was 0.948 in 10 healthy volunteers and 0.981 in 10 subjects with unilateral ACL rupture. Intrarater reliability in the volunteers was 0.829.

CONCLUSIONS

By use of the developed measurement device, the "Laxitester" (ORTEMA Sport Protection, Markgroeningen, Germany), objective differentiation between isolated ACL rupture and ACL rupture plus additional medial instability is possible. Values for anterior translation are reliable and reproducible by different examiners and by the same examiner at different times.

CLINICAL RELEVANCE

The Laxitester allows objectification of medial instability in combination with ACL injuries and provides a reference regarding the need for additional medial stabilization. Compared with the isolated measurement of anteroposterior translation, knee instability can be assessed in a more differentiated manner.

An original clinical methodology for non-invasive assessment of pivot-shift test

Even if pivot-shift (PS) test has been clinically used to specifically detect anterior cruciate ligament (ACL) injury, the main problem in using this combined test has been yet associated with the difficulty of clearly quantifying its outcome. The goal of this study was to describe an original non-invasive methodology used to quantify PS test, highlighting its possible clinical reliability. The method was validated on 66 consecutive unilateral ACL-injured patients. A commercial triaxial accelerometer was non-invasively mounted on patient's tibia, the corresponding 3D acceleration was acquired during PS test execution and a set of specific parameters were automatically identified on the signal to quantify the test. PS test was repeated three times on both injured and controlateral limbs. Reliability of the method was found to be good (mean intra-rater intraclass correlation coefficient was 0.79); moreover, we found that ACL-deficient knees presented statistically higher values for the identified parameters--than the controlateral healthy limbs, averagely reporting also large effect size.

In vitro and intraoperative laxities after single-bundle and double-bundle anterior cruciate ligament reconstructions

PURPOSE

The purpose of this study was to objectively evaluate whether double-bundle anterior cruciate ligament (ACL) reconstruction can better restore the normal translational and rotational laxities than the conventional single-bundle ACL reconstruction among the reported biomechanical studies.

METHODS

A systematic literature search was conducted to identify in vitro and in vivo (intraoperative) biomechanical studies that compared the laxities (anterior or anteroposterior or rotational) between single- and double-bundle ACL reconstructions. Because of large variability among the loading conditions and testing methods used to determine the rotational laxities among the studies, a meta-analysis of rotational laxities was not feasible.

RESULTS

Seven in vitro and three in vivo studies were included in this analysis based on the predefined inclusion criteria. The overall mean differences calculated by the random effects model in anteroposterior laxity between the single-bundle and double-bundle ACL reconstruction techniques at 0°, 30°, 60°, and 90° of flexion were 0.99 mm, 0.38 mm, 0.34 mm, and 0.07 mm, respectively. No statistically significant difference was noted between the 2 treatments at all flexion angles. Among the 9 studies that compared the rotational laxity of single-bundle and double-bundle ACL reconstructions, 4 reported that double-bundle reconstruction can provide better rotational control than single-bundle reconstruction. The other 5 studies could not identify any significant difference between the 2 reconstructions in terms of rotational laxity.

CONCLUSIONS

Both single- and double-bundle treatment options for ACL injury result in similar anteroposterior knee joint laxity at time 0. No conclusive evidence on the superiority of 1 reconstruction technique over the other in terms of rotation laxity can be obtained because of several variations in the experimental protocol and the kinematics used to measure the rotational laxity among the studies.

LEVEL OF EVIDENCE

Level III, meta-analysis.

A new diagnostic approach using regional analysis of anterior knee laxity in patients with anterior cruciate ligament deficiency

PURPOSE

The first purpose of this study was to analyze the characteristics of the anterior knee laxity in the three regions of different stiffness in the force-displacement curve, which was obtained from a frequently used arthrometer for quantifying knee joint stability in the patients with anterior cruciate ligament (ACL) rupture and the healthy controls. The second purpose was to compare the characteristics from the regional analysis of the anterior knee laxity between the two subject groups in order to explore proper diagnosis criteria.

METHODS

Seventy-one patients with unilateral ACL tear and eighty healthy controls were enrolled and their anterior knee laxities were tested using the KT-2000 arthrometer. The displacements and stiffness of the three regions were extracted separately and compared between groups to further develop the diagnostic criteria.

RESULTS

The results indicated that the laxity behavior was mostly affected in Region 2 and Region 3 after ACL tear. Two good indicators for ACL tear were found in the receiver operating characteristic (ROC) curve analysis: Region 2 with the displacement larger than 3.7 mm and Region 3 with the stiffness smaller than 22 N/mm. These two criteria provided a better diagnostic accuracy with increased sensitivity.

CONCLUSIONS

The regional analysis method developed in this study could provide more information for understanding the characteristics of the anterior knee laxity and help increase the diagnostic accuracy for ACL rupture.

LEVEL OF EVIDENCE

II.

Initial evaluation of posterior cruciate ligament injuries: history, physical examination, imaging studies, surgical and nonsurgical indications

Compared with anterior cruciate ligament injuries, posterior cruciate ligament injuries are a rare event. The mechanisms are predictable and a thorough physical examination is mandatory to rule out or define combined injury patterns. Stress radiography and magnetic resonance imaging studies are very helpful adjuncts. Acute and chronic injuries require slightly different approaches. As our understanding of normal and pathologic knee joint kinematics develops, nonoperative rehabilitation goals and operative techniques continue to evolve.