Measurement of in vivo anterior cruciate ligament strain during dynamic jump landing

Lower-Extremity Kinematics Differed Between a Controlled Drop-Jump and Volleyball-Takeoffs

Previous studies utilizing jump-landing biomechanics to predict anterior cruciate ligament injuries have shown inconsistent findings. The purpose of this study was to quantify the differences and correlations in jump-landing kinematics between a drop-jump, a controlled volleyball-takeoff, and a simulated-game volleyball-takeoff. Seventeen female volleyball players performed these 3 tasks on a volleyball court, while 3-dimensional kinematic data were collected by 3 calibrated camcorders. Participants demonstrated significantly increased jump height, shorter stance time, increased time differences in initial contact between 2 feet, increased knee and hip flexion at initial contact and decreased peak knee and hip flexion for both left and right legs, and decreased knee–ankle distance ratio at the lowest height of midhip for the 2 volleyball-takeoffs compared with the drop-jump (P < .05, Cohen’s dz ≥ 0.8). Significant correlations were observed for all variables between the 2 volleyball-takeoffs (P < .05, ρ ≥ .6) but were not observed for most variables between the drop-jump and 2 volleyball-takeoffs. Controlled drop-jump kinematics may not represent jump-landing kinematics exhibited during volleyball competition. Jump-landing mechanics during sports-specific tasks may better represent those exhibited during sports competition and their associated risk of anterior cruciate ligament injury compared with the drop-jump.

Determination of the Position of the Knee at the Time of an Anterior Cruciate Ligament Rupture for Male Versus Female Patients by an Analysis of Bone Bruises

BACKGROUND

The incidence of anterior cruciate ligament (ACL) ruptures is 2 to 4 times higher in female athletes as compared with their male counterparts. As a result, a number of recent studies have addressed the hypothesis that female and male patients sustain ACL injuries via different mechanisms. The efficacy of prevention programs may be improved by a better understanding of whether there are differences in the injury mechanism between sexes. Hypothesis/Purpose: To compare knee positions at the time of a noncontact ACL injury between sexes. It was hypothesized that there would be no differences in the position of injury.

STUDY DESIGN

Controlled laboratory study.

METHODS

Clinical T2-weighted magnetic resonance imaging (MRI) scans from 30 participants (15 male and 15 female) with a noncontact ACL rupture were reviewed retrospectively. MRI scans were obtained within 1 month of injury. Participants had contusions associated with an ACL injury on both the medial and lateral articular surfaces of the femur and tibia. Three-dimensional models of the femur, tibia, and associated bone bruises were created via segmentation on MRI. The femur was positioned relative to the tibia to maximize bone bruise overlap, thereby predicting the bone positions near the time of the injury. Flexion, valgus, internal tibial rotation, and anterior tibial translation were measured in the predicted position of injury.

RESULTS

No statistically significant differences between male and female patients were detected in the position of injury with regard to knee flexion ( P = .66), valgus ( P = .87), internal tibial rotation ( P = .26), or anterior tibial translation ( P = .18).

CONCLUSION

These findings suggest that a similar mechanism results in an ACL rupture in both male and female athletes with this pattern of bone bruising.

CLINICAL RELEVANCE

This study provides a novel comparison of male and female knee positions at the time of an ACL injury that may offer information to improve injury prevention strategies.

An extended OpenSim knee model for analysis of strains of connective tissues

Background

OpenSim musculoskeletal models provide an accurate simulation environment that eases limitations of in vivo and in vitro studies. In this work, a biomechanical knee model was formulated with femoral articular cartilages and menisci along with 25 connective tissue bundles representing ligaments and capsules. The strain patterns of the connective tissues in the presence of femoral articular cartilage and menisci in the OpenSim knee model was probed in a first of its kind study.

Methods

The effect of knee flexion (0°–120°), knee rotation (− 40° to 30°) and knee adduction (− 15° to 15°) on the anterior cruciate, posterior cruciate, medial collateral, lateral collateral ligaments and other connective tissues were studied by passive simulation. Further, a new parameter for assessment of strain namely, the differential inter-bundle strain of the connective tissues were analyzed to provide new insights for injury kinematics.

Results

ACL, PCL, LCL and PL was observed to follow a parabolic strain pattern during flexion while MCL represented linear strain patterns. All connective tissues showed non-symmetric parabolic strain variation during rotation. During adduction, the strain variation was linear for the knee bundles except for FL, PFL and TL.

Conclusions

Strains higher than 0.1 were observed in most of the bundles during lateral rotation followed by abduction, medial rotation and adduction. In the case of flexion, highest strains were observed in aACL and aPCL. A combination of strains at a flexion of 0° with medial rotation of 30° or a flexion of 80° with rotation of 30° are evaluated as rupture-prone kinematics.

Electronic supplementary material

The online version of this article (10.1186/s12938-018-0474-8) contains supplementary material, which is available to authorized users.

Landing Styles Influences Reactive Strength Index without Increasing Risk for Injury

The aim was to determine which three landing styles - stiff (ST), self-selected (SS), or soft (SF) - exhibit safer landing mechanics and greater jumping performance. Thirty participants (age: 26.5±5.1 years; height: 171.0±8.8 cm; weight: 69.7±10.1 kg) performed five trials of three randomized drop jump (40 cm) landing styles including SF (~60° knee flexion), ST (knees as straight as possible), and SS. Knee flexion and valgus angles and kinetics were measured. An electromyography system measured muscle activity of the gluteus maximus, quadriceps, hamstrings, tibialis anterior, and gastrocnemius. Reactive strength index (RSI) was used to measure jumping performance. ANOVAs were used to compare the three landings. All landings differed in knee flexion (p<0.001; effect size (η 2 ): 0.9) but not valgus (p=.13; η 2 :.15). RSI (mm·ms -1 ) showed differences for all jumps (p<0.001; η 2 : 0.7) with SS (0.96) showing the highest value, then ST (0.93), and SF (0.64). Ground reaction forces were different between jumps (p<0.001; η 2 : 0.4) with SF (1.34/bodyweight (bw)) showing lower forces, then SS (1.50/bw), and ST (1.81/bw). No between-jump differences were observed for EMG (p>0.66; η 2 : 0.3). No landing demonstrated valgus landing mechanics. The SS landing exhibited the highest RSI. However, the 1.8/bw exhibited by the ST landing might contribute to overload of musculotendinous structures at the knee.

An In Vivo Prediction of Anisometry and Strain in Anterior Cruciate Ligament Reconstruction - A Combined Magnetic Resonance and Dual Fluoroscopic Imaging Analysis

PURPOSE

To evaluate the in vivo anisometry and strain of theoretical anterior cruciate ligament (ACL) grafts in the healthy knee using various socket locations on both the femur and tibia.

METHODS

Eighteen healthy knees were imaged using magnetic resonance imaging and dual fluoroscopic imaging techniques during a step-up and sit-to-stand motion. The anisometry of the medial aspect of the lateral femoral condyle was mapped using 144 theoretical socket positions connected to an anteromedial, central, and posterolateral attachment site on the tibia. The 3-dimensional wrapping paths of each theoretical graft were measured. Comparisons were made between the anatomic, over the top (OTT), and most-isometric (isometric) femoral socket locations, as well as between tibial insertions.

RESULTS

The area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. The most isometric attachment site was found midway on the Blumensaat line with approximately 2% and 6% strain during the step-up and sit-to-stand motion, respectively. Posterior femoral attachments resulted in decreased graft lengths with increasing flexion angles, whereas anterodistal attachments yielded increased lengths with increasing flexion angles. The anisometry of the anatomic, OTT and isometric grafts varied between tibial insertions (P < .001). The anatomic graft was significantly more anisometric than the OTT and isometric graft at deeper flexion angles (P < .001).

CONCLUSIONS

An area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. ACL reconstruction at the isometric and OTT location resulted in nonanatomic graft behavior, which could overconstrain the knee at deeper flexion angles. Tibial location significantly affected graft strains for the anatomic, OTT, and isometric socket location. CLINICAL RELEVANCE: This study improves the knowledge on ACL anisometry and strain and helps surgeons to better understand the consequences of socket positioning during intra-articular ACL reconstruction.

Lowering minimum eye height to increase peak knee and hip flexion during landing

The purpose was to determine the effect of lowering minimum eye height through an externally focused object on knee and hip flexion and impact forces during jump-landing. Kinematics and ground reaction forces were collected when 20 male and 19 female participants performed jump-landing trials with their natural minimum eye height, and trials focusing on lowering their minimum eye height to an external object, which was set at 5% or 10% of standing height lower. Participants demonstrated decreased minimum eye height and increased peak knee and hip flexion during early-landing and stance phase when focusing on lowering eye height to the external object (p < 0.01). Peak vertical ground reaction forces during early-landing also decreased for the greater force group (p < 0.001). Jump-landing training through manipulating eye height provides a strategy that involves an external focus and intrinsic feedback, which may have advantages in promoting learning and practical application.

Dynamically tensioned ACL functional knee braces reduce ACL and meniscal strain

PURPOSE

The effectiveness of ACL functional knee braces to reduce meniscal and ACL strain after ACL injury or reconstruction is not well understood. A new dynamic knee tensioning brace system has been designed to apply an active stabilizing force to the knee. The ability of this system to reduce tissue strains is unknown. The purpose of this study was to test the ability of the dynamically tensioned brace to reduce strain in both the ACL and meniscus during rehabilitation activities.

METHODS

A combined in vivo/in silico/in vitro method was used to study three activities: gait, double leg squat, and single leg squat. Muscle forces and kinematics for each activity were derived through in vivo motion capture and applied to seven cadaveric knee specimens fitted with custom braces. Medial meniscal strain and ACL strain were measured in ACL intact, deficient and reconstructed conditions.

RESULTS

The brace lowered peak and average meniscal strain in ACL deficient knees (P < 0.05) by an average of 1.7%. The brace was also found to lower meniscal strain in reconstructed knees (1.1%) and lower ACL strain in ACL intact (1.3%) and reconstructed knees (1.4%) (P < 0.05).

CONCLUSIONS

This study supports the use of a brace equipped with a dynamic tensioning system to lower meniscal strain in ACL-deficient knees. Its use may help decrease the risk of subsequent meniscal tears in chronic ACL deficiency or delayed reconstruction. In ACL-intact and reconstructed knees, the brace may be beneficial in injury prophylaxis or in protecting the ACL graft following reconstruction. These results will aid clinicians make informed recommendations for functional brace use in patients with unstable knees.

LEVEL OF EVIDENCE

II.

In vivo mechanical behaviour of the anterior cruciate ligament: A study of six daily and high impact activities

The anterior cruciate ligament (ACL) plays a key role in the stability of the knee joint restricting the rotation and anterior tibial translation. However, there is a lack of knowledge of the in vivo ACL mechanical behaviour during high impact manoeuvres. The motion of 12 young participants with healthy knees was captured while they performed the following activities: walking, running, cross-over cutting, sidestep cutting, jumping and jumping with one leg. The in vivo ACL length and strain were estimated using experimental kinematic data and three degree of freedom (DOF) knee model. The in vivo ACL tensile forces were determined with a well-established force/strain relationship obtained through ACL tensile tests. Statistical regression models between ACL length with respect to angles for each activity have been performed in order to better understand the ACL failure mechanisms. The maximum ACL tensile force was observed during jumping vertically at maximum effort with two legs (1.076±0.113 N/BW). Surprisingly, the peak tensile ACL force for all subjects during crossover cutting (0.715±0.2647 N/BW) was lower than during walking (0.774±0.064 N/BW). Regression coefficients for crossover cutting indicated that excessive knee rotation and abduction angles contribute more significantly to the ACL elongation than in activities such as walking or running. These findings suggested that the ACL is subjected to multidirectional loading; further studies will be performed to investigate torsion, tensile and shear force on the ligament.

Fatigue injury risk in anterior cruciate ligament of target side knee during golf swing

A golf-related ACL injury can be linked with excessive golf play or practice because such over-use by repetitive golf swing motions can increase damage accumulation to the ACL bundles. In this study, joint angular rotations, forces, and moments, as well as the forces and strains on the ACL of the target-side knee joint, were investigated for ten professional golfers using the multi-body lower extremity model. The fatigue life of the ACL was also predicted by assuming the estimated ACL force as a cyclic load. The ACL force and strain reached their maximum values within a short time just after ball-impact in the follow-through phase. The smaller knee flexion, higher internal tibial rotation, increase of the joint compressive force and knee abduction moment in the follow-through phase were shown as to lead an increased ACL loading. The number of cycles to fatigue failure (fatigue life) in the ACL might be several thousands. It is suggested that the excessive training or practice of swing motion without enough rest may be one of factors to lead to damage or injury in the ACL by the fatigue failure. The present technology can provide fundamental information to understand and prevent the ACL injury for golf players.

The influence of muscle-tendon forces on ACL loading during jump landing: a systematic review

BACKGROUND

The goal of this review is to summarise and discuss the reported influence of muscle-tendon forces on anterior cruciate ligament (ACL) loading during the jump-landing task by means of biomechanical analyses of the healthy knee.

METHODS

A systematic review of the literature was conducted using different combinations of the terms "knee", "ligament", "load", "tension ", "length", "strain", "elongation" and "lengthening". 26 original articles (n=16 in vitro studies; n=10 in situ studies) were identified which complied with all inclusion/exclusion criteria.

RESULTS

No apparent trend was found between ACL loading and the ratio between hamstrings and quadriceps muscle-tendon forces prior to or during landing. Four in vitro studies reported reduced peak ACL strain if the quadriceps force was increased; while one in vitro study and one in situ study reported reduced ACL loading if the hamstrings force was increased. A meta-analysis of the reported results was not possible because of the heterogeneity of the confounding factors.

CONCLUSION

The reported results suggest that increased hip flexion during landing may help in reducing ACL strain by lengthening the hamstrings, and thus increasing its passive resistance to stretch. Furthermore, it appears that increased tensile stiffness of the quadriceps may help in stabilising the knee joint during landing, and thus protecting the passive soft-tissue structures from overloading.

LEVEL OF EVIDENCE

Ib.

Changing Sagittal-Plane Landing Styles to Modulate Impact and Tibiofemoral Force Magnitude and Directions Relative to the Tibia

CONTEXT

Ground reaction force (GRF) and tibiofemoral force magnitudes and directions have been shown to affect anterior cruciate ligament loading during landing. However, the kinematic and kinetic factors modifying these 2 forces during landing are unknown.

OBJECTIVE

To clarify the intersegmental kinematic and kinetic links underlying the alteration of the GRF and tibiofemoral force vectors secondary to changes in the sagittal-plane body position during single-legged landing.

DESIGN

Crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty recreationally active participants (age = 23.4 ± 3.6 years, height = 171.0 ± 9.4 cm, mass = 73.3 ± 12.7 kg).

INTERVENTION(S)

Participants performed single-legged landings using 3 landing styles: self-selected landing (SSL), body leaning forward and landing on the toes (LFL), and body upright with flat-footed landing (URL). Three-dimensional kinetics and kinematics were recorded.

MAIN OUTCOME MEASURE(S)

Sagittal-plane tibial inclination and knee-flexion angles, GRF magnitude and inclination angles relative to the tibia, and proximal tibial forces at peak tibial axial forces.

RESULTS

The URL resulted in less time to peak tibial axial forces, smaller knee-flexion angles, and greater magnitude and a more anteriorly inclined GRF vector relative to the tibia than did the SSL. These changes led to the greatest peak tibial axial and anterior shear forces in the URL among the 3 landing styles. Conversely, the LFL resulted in longer time to peak tibial axial forces, greater knee-flexion angles, and reduced magnitude and a more posteriorly inclined GRF vector relative to the tibia than the SSL. These changes in LFL resulted in the lowest peak tibial axial and largest posterior shear forces among the 3 landing styles.

CONCLUSIONS

Sagittal-plane intersegmental kinematic and kinetic links strongly affected the magnitude and direction of GRF and tibiofemoral forces during the impact phase of single-legged landing. Therefore, improving sagittal-plane landing mechanics is important in reducing harmful magnitudes and directions of impact forces on the anterior cruciate ligament.

Lower Extremity Movement Differences Persist After Anterior Cruciate Ligament Reconstruction and When Returning to Sports

OBJECTIVE

To examine how landing mechanics change in patients after anterior cruciate ligament reconstruction (ACL-R) between 6 months and 12 months after surgery.

DESIGN

Case-series.

SETTING

Laboratory.

PARTICIPANTS

Fifteen adolescent patients after ACL-R participated.

INTERVENTIONS

Lower extremity three-dimensional motion analysis was conducted during a bilateral stop jump task in patients at 6 and 12 months after ACL-R. Joint kinematic and kinetic data, in addition to ground reaction forces, were collected at each time point.

MAIN OUTCOME MEASURES

During the stop jump landing, the peak joint moments and the initial and peak joint motion at the ankle, knee, and hip were examined. The peak vertical ground reaction force was also examined.

RESULTS

Interactions were observed for both the peak knee (P = 0.03) and hip extension moment (P = 0.07). However, only the hip extension moment was symmetrical level at 12 months. Statistically significant (P < 0.05) side-to-side differences existed for the ankle angle at initial contact, peak plantarflexion moment, peak hip flexion angle, and peak impact vertical ground reaction force independent of time.

CONCLUSIONS

The findings of this study suggest that sagittal plane moments at the knee and hip demonstrate an increase in symmetry between 6 months and 1 year after ACL-R surgery, however, symmetry of the knee extension moment is not established by 12 months after surgery. The lack of change in the variables across time was unexpected. As a result, it is inappropriate to expect a change in landing mechanics solely as a result of time alone after discharge from rehabilitation.

Accuracy of model-based tracking of knee kinematics and cartilage contact measured by dynamic volumetric MRI

The purpose of this study was to determine the accuracy of knee kinematics and cartilage contact measured by volumetric dynamic MRI. A motor-actuated phantom drove femoral and tibial bone segments through cyclic 3D motion patterns. Volumetric images were continuously acquired using a 3D radially undersampled cine spoiled gradient echo sequence (SPGR-VIPR). Image data was binned based on position measured via a MRI-compatible rotary encoder. High-resolution static images were segmented to create bone models. Model-based tracking was performed by optimally registering the bone models to the volumetric images at each frame of the SPGR-VIPR series. 3D tibiofemoral translations and orientations were reconstructed, and compared to kinematics obtained by tracking fiducial markers. Imaging was repeated on a healthy subject who performed cyclic knee flexion-extension. Cartilage contact for the subject was assessed by measuring the overlap between articular cartilage surfaces. Model-based tracking was able to track tibiofemoral angles and translations with precisions less than 0.8° and 0.5mm. These precisions resulted in an uncertainty of less than 0.5mm in cartilage contact location. Dynamic SPGR-VIPR imaging can accurately assess in vivo knee kinematics and cartilage contact during voluntary knee motion performed in a MRI scanner. This technology could facilitate the quantitative investigation of links between joint mechanics and the development of osteoarthritis.

Efficacy of ACL injury risk screening methods in identifying high-risk landing patterns during a sport-specific task

Screening methods sensitive to movement strategies that increase anterior cruciate ligament (ACL) loads are likely to be effective in identifying athletes at-risk of ACL injury. Current ACL injury risk screening methods are yet to be evaluated for their ability to identify athletes' who exhibit high-risk lower limb mechanics during sport-specific maneuvers associated with ACL injury occurrences. The purpose of this study was to examine the efficacy of two ACL injury risk screening methods in identifying high-risk lower limb mechanics during a sport-specific landing task. Thirty-two female athletes were screened using the Landing Error Scoring System (LESS) and Tuck Jump Assessment. Participants' also completed a sport-specific landing task, during which three-dimensional kinematic and kinetic data were collected. One-dimensional statistical parametric mapping was used to examine the relationships between screening method scores, and the three-dimensional hip and knee joint rotation and moment data from the sport-specific landing. Higher LESS scores were associated with reduced knee flexion from 30 to 57 ms after initial contact (P = 0.003) during the sport-specific landing; however, no additional relationships were found. These findings suggest the LESS and Tuck Jump Assessment may have minimal applicability in identifying athletes' who exhibit high-risk landing postures in the sport-specific task examined.

A comparison of hamstring muscle activity during different screening tests for non-contact ACL injury

BACKGROUND

Reduced ability to activate the medial hamstring muscles during a sports-specific sidecutting movement has been found to be a potential risk factor for non-contact ACL injury. However, whether a reduced ability to activate the medial hamstring muscle is a general neuromuscular phenomenon and thereby observable independently of the type of clinical screening tests used is not known. This cross sectional study investigated the rank correlation of knee joint neuromuscular activity between three different ACL injury risk screening tests.

METHODS

Sixty-two adolescent female elite football and handball players (16.7±1.3years) participated in the study. Using surface electromyography (EMG) assessment, the neuromuscular activity of medial hamstring muscle (semitendinosus, ST), lateral hamstring muscle (biceps femoris, BF) and quadriceps muscle (vastus lateralis, VL) were monitored during three standardized screening tests - i.e. one-legged horizontal hop (OLH), drop vertical jump (DJ) and sidecutting (SC). Neuromuscular pre-activity was measured in the time interval 10ms prior to initial contact on a force plate.

RESULTS

For neuromuscular hamstring muscle pre-activity, correlation analysis (Spearman correlation coefficient) showed low-to-moderate correlations between SC and 1) DJ (rs=0.34-0.36, P<0.05) and 2) OLH (rs=0.40-0.41, P<0.05), respectively.

CONCLUSIONS

In conclusion, the present data suggest that hamstring pre-activity share some common variance during the examined tests. However, a lack of strong correlation suggests that we cannot generalize one risk factor during one test to another test.

CLINICAL RELEVANCE

The present data demonstrate that one-legged horizontal hop and drop vertical jump testing that are commonly used in the clinical setting does not resemble the specific neuromuscular activity patterns known to exist during sidecutting, a well known high risk movement for non-contact ACL injury.

A Systematic Evaluation of Field-Based Screening Methods for the Assessment of Anterior Cruciate Ligament (ACL) Injury Risk

BACKGROUND

Laboratory-based measures provide an accurate method to identify risk factors for anterior cruciate ligament (ACL) injury; however, these methods are generally prohibitive to the wider community. Screening methods that can be completed in a field or clinical setting may be more applicable for wider community use. Examination of field-based screening methods for ACL injury risk can aid in identifying the most applicable method(s) for use in these settings.

OBJECTIVE

The objective of this systematic review was to evaluate and compare field-based screening methods for ACL injury risk to determine their efficacy of use in wider community settings.

DATA SOURCES

An electronic database search was conducted on the SPORTDiscus™, MEDLINE, AMED and CINAHL databases (January 1990-July 2015) using a combination of relevant keywords. A secondary search of the same databases, using relevant keywords from identified screening methods, was also undertaken.

STUDY SELECTION

Studies identified as potentially relevant were independently examined by two reviewers for inclusion. Where consensus could not be reached, a third reviewer was consulted. Original research articles that examined screening methods for ACL injury risk that could be undertaken outside of a laboratory setting were included for review.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently assessed the quality of included studies. Included studies were categorized according to the screening method they examined. A description of each screening method, and data pertaining to the ability to prospectively identify ACL injuries, validity and reliability, recommendations for identifying 'at-risk' athletes, equipment and training required to complete screening, time taken to screen athletes, and applicability of the screening method across sports and athletes were extracted from relevant studies.

RESULTS

Of 1077 citations from the initial search, a total of 25 articles were identified as potentially relevant, with 12 meeting all inclusion/exclusion criteria. From the secondary search, eight further studies met all criteria, resulting in 20 studies being included for review. Five ACL-screening methods-the Landing Error Scoring System (LESS), Clinic-Based Algorithm, Observational Screening of Dynamic Knee Valgus (OSDKV), 2D-Cam Method, and Tuck Jump Assessment-were identified. There was limited evidence supporting the use of field-based screening methods in predicting ACL injuries across a range of populations. Differences relating to the equipment and time required to complete screening methods were identified.

LIMITATIONS

Only screening methods for ACL injury risk were included for review. Field-based screening methods developed for lower-limb injury risk in general may also incorporate, and be useful in, screening for ACL injury risk.

CONCLUSIONS

Limited studies were available relating to the OSDKV and 2D-Cam Method. The LESS showed predictive validity in identifying ACL injuries, however only in a youth athlete population. The LESS also appears practical for community-wide use due to the minimal equipment and set-up/analysis time required. The Clinic-Based Algorithm may have predictive value for ACL injury risk as it identifies athletes who exhibit high frontal plane knee loads during a landing task, but requires extensive additional equipment and time, which may limit its application to wider community settings.

Relationship Between Force Production During Isometric Squats and Knee Flexion Angles During Landing

Decreased knee flexion angles during landing are associated with increased anterior cruciate ligament loading. The underlying mechanisms associated with decreased self-selected knee flexion angles during landing are still unclear. The purpose of this study was to establish the relationship between the peak force production at various knee flexion angles (35, 55, 70, and 90°) during isometric squats and the actual knee flexion angles that occur during landing in both men and women. A total of 18 men and 18 women recreational/collegiate athletes performed 4 isometric squats at various knee flexion angles while vertical ground reaction forces were recorded. Participants also performed a jump-landing-jump task while lower extremity kinematics were collected. For women, significant correlations were found between the peak force production at 55 and 70° of knee flexion during isometric squats and the knee flexion angle at initial contact of landing. There were also significant correlations between the peak force production at 55, 70, and 90° of knee flexion during isometric squats and the peak knee flexion angle during landing. These correlations tended to be stronger during isometric squats at greater knee flexion compared with smaller knee flexion. No significant correlations were found for men. Posture-specific strength may play an important role in determining self-selected knee flexion angles during landing for women.

Knee Kinematics During Noncontact Anterior Cruciate Ligament Injury as Determined From Bone Bruise Location

BACKGROUND

The motions causing noncontact anterior cruciate ligament (ACL) injury remain unclear. Tibiofemoral bone bruises are believed to be the result of joint impact near the time of ACL rupture. The locations and frequencies of these bone bruises have been reported, but there are limited data quantifying knee position and orientation near the time of injury based on these contusions.

HYPOTHESIS

Knee position and orientation near the time of noncontact ACL injury include extension and anterior tibial translation.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Magnetic resonance images of 8 subjects with noncontact ACL injuries were acquired within 1 month of injury and were subsequently analyzed. All subjects exhibited bruises on both the femur and tibia in both medial and lateral compartments. The outer margins of bone and the bone bruise surfaces were outlined on each image to create a 3-dimensional model of each subject's knee in its position during magnetic resonance imaging (MRI position). Numerical optimization was used to maximize overlap of the bone bruises on the femur and tibia and to predict the position of injury. Flexion angle, valgus orientation, internal tibial rotation, and anterior tibial translation were measured in both the MRI position and the predicted position of injury. Differences in kinematics between the MRI position, which served as an unloaded reference, and the predicted position of injury were compared by use of paired t tests.

RESULTS

Flexion angle was near full extension in both the MRI position and the predicted position of injury (8° vs 12°; P = .2). Statistically significant increases in valgus orientation (5°; P = .003), internal tibial rotation (15°; P = .003), and anterior tibial translation (22 mm; P < .001) were observed in the predicted position of injury relative to the MRI position.

CONCLUSION

These results suggest that for the bone bruise pattern studied, landing on an extended knee is a high risk for ACL injury. Extension was accompanied by increased anterior tibial translation (22 mm), internal tibial rotation (15°), and valgus rotation (5°) in the predicted position of injury relative to the MRI position.

CLINICAL RELEVANCE

This study provides novel data characterizing the motions associated with ACL injury, information critical to improving strategies aimed at injury prevention.

Mapping of contributions from collateral ligaments to overall knee joint constraint: an experimental cadaveric study

Understanding the contribution of the soft-tissues to total joint constraint (TJC) is important for predicting joint kinematics, developing surgical procedures, and increasing accuracy of computational models. Previous studies on the collateral ligaments have focused on quantifying strain and tension properties under discrete loads or kinematic paths; however, there has been little work to quantify collateral ligament contribution over a broad range of applied loads and range of motion (ROM) in passive constraint. To accomplish this, passive envelopes were collected from nine cadaveric knees instrumented with implantable pressure transducers (IPT) in the collateral ligaments. The contributions from medial and lateral collateral ligaments (LCL) were quantified by the relative contribution of each structure at various flexion angles (0-120 deg) and compound external loads (±10 N m valgus, ±8 N m external, and ±40 N anterior). Average medial collateral ligament (MCL) contributions were highest under external and valgus torques from 60 deg to 120 deg flexion. The MCL showed significant contributions to TJC under external torques throughout the flexion range. Average LCL contributions were highest from 0 deg to 60 deg flexion under external and varus torques, as well as internal torques from 60 deg to 110 deg flexion. Similarly, these regions were found to have statistically significant LCL contributions. Anterior and posterior loads generally reduced collateral contribution to TJC; however, posterior loads further reduced MCL contribution, while anterior loads further reduced LCL contribution. These results provide insight to the functional role of the collaterals over a broad range of passive constraint. Developing a map of collateral ligament contribution to TJC may be used to identify the effects of injury or surgical intervention on soft-tissue, and how collateral ligament contributions to constraint correlate with activities of daily living.

In vivo measurement of localized tibiofemoral cartilage strains in response to dynamic activity

BACKGROUND

Altered local mechanical loading may disrupt normal cartilage homeostasis and play a role in the progression of osteoarthritis. Currently, there are limited data quantifying local cartilage strains in response to dynamic activity in normal or injured knees.

PURPOSE/HYPOTHESIS

To directly measure local tibiofemoral cartilage strains in response to a dynamic hopping activity in normal healthy knees. We hypothesized that local regions of cartilage will exhibit significant compressive strains in response to hopping, while overall compartmental averages may not.

STUDY DESIGN

Controlled laboratory study.

METHODS

Both knees of 8 healthy subjects underwent magnetic resonance imaging before and immediately after a dynamic hopping activity. Images were segmented and then used to create 3-dimensional surface models of bone and cartilage. These pre- and postactivity models were then registered using an iterative closest point technique to enable site-specific measurements of cartilage strain (defined as the normalized change in cartilage thickness before and after activity) on the femur and tibia.

RESULTS

Significant strains were observed in both the medial and lateral tibial cartilage, with each compartment averaging a decrease of 5%. However, these strains varied with location within each compartment, reaching a maximum compressive strain of 8% on the medial plateau and 7% on the lateral plateau. No significant averaged compartmental strains were observed in the medial or lateral femoral cartilage. However, local regions of the medial and lateral femoral cartilage experienced significant compressive strains, reaching maximums of 6% and 3%, respectively.

CONCLUSION

Local regions of both the femur and tibia experienced significant cartilage strains as a result of dynamic activity. An understanding of changes in cartilage strain distributions may help to elucidate the biomechanical factors contributing to cartilage degeneration after joint injury.

CLINICAL RELEVANCE

Site-specific measurements of in vivo cartilage strains are important because altered loading is believed to be a factor contributing to the development and progression of osteoarthritis. Specifically, this methodology and data could be used to evaluate the effects of soft tissue injuries (such as ligament or meniscus tears) on cartilage strains in response to dynamic activities of daily living.

The effects of 2 landing techniques on knee kinematics, kinetics, and performance during stop-jump and side-cutting tasks

BACKGROUND

Anterior cruciate ligament injuries (ACL) commonly occur during jump landing and cutting tasks. Attempts to land softly and land with greater knee flexion are associated with decreased ACL loading. However, their effects on performance are unclear.

HYPOTHESIS

Attempts to land softly will decrease peak posterior ground-reaction force (PPGRF) and knee extension moment at PPGRF compared with a natural landing during stop-jump and side-cutting tasks. Attempts to land with greater knee flexion at initial ground contact will increase knee flexion at PPGRF compared with a natural landing during both tasks. In addition, both landing techniques will increase stance time and lower extremity mechanical work as well as decrease jump height and movement speed compared with a natural landing during both tasks.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 18 male and 18 female recreational athletes participated in the study. Three-dimensional kinematic and kinetic data were collected during stop-jump and side-cutting tasks under 3 conditions: natural landing, soft landing, and landing with greater knee flexion at initial ground contact.

RESULTS

Attempts to land softly decreased PPGRF and knee extension moment at PPGRF compared with a natural landing during stop-jump tasks. Attempts to land softly decreased PPGRF compared with a natural landing during side-cutting tasks. Attempts to land with greater knee flexion at initial ground contact increased knee flexion angle at PPGRF compared with a natural landing during both stop-jump and side-cutting tasks. Attempts to land softly and land with greater knee flexion at initial ground contact increased stance time and lower extremity mechanical work, as well as decreased jump height and movement speed during both stop-jump and side-cutting tasks.

CONCLUSION

Although landing softly and landing with greater knee flexion at initial ground contact may reduce ACL loading during stop-jump and side-cutting tasks, the performance of these tasks decreased, as indicated by increased stance time and mechanical work as well as decreased jump height and movement speed.

CLINICAL RELEVANCE

Training effects tested in laboratory environments with the focus on reducing ACL loading may be reduced in actual competition environments when the focus is on athlete performance. The effects of training programs for ACL injury prevention on lower extremity biomechanics in athletic tasks may need to be evaluated in laboratories as well as in actual competitions.

What is normal? Female lower limb kinematic profiles during athletic tasks used to examine anterior cruciate ligament injury risk: a systematic review

BACKGROUND

It has been proposed that the performance of athletic tasks where normal motion is exceeded has the potential to damage the anterior cruciate ligament (ACL). Determining the expected or 'normal' kinematic profile of athletic tasks commonly used to assess ACL injury risk can provide an evidence base for the identification of abnormal or anomalous task performances in a laboratory setting.

OBJECTIVE

The objective was to conduct a systematic review of studies examining lower limb kinematics of females during drop landing, drop vertical jump, and side-step cutting tasks, to determine 'normal' ranges for hip and knee joint kinematic variables.

DATA SOURCES

An electronic database search was conducted on the SPORTDiscus(TM), MEDLINE, AMED and CINAHL (January 1980-August 2013) databases using a combination of relevant keywords.

STUDY SELECTION

Studies identified as potentially relevant were independently examined by two reviewers for inclusion. Where consensus could not be reached, a third reviewer was consulted. Original research articles that examined three-dimensional hip and knee kinematics of female subjects during the athletic tasks of interest were included for review. Articles were excluded if subjects had a history of lower back or lower limb joint injury or isolated data from the female cohort could not be extracted.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently assessed the quality of included studies. Data on subject characteristics, the athletic task performed, and kinematic data were extracted from included studies. Studies were categorised according to the athletic task being examined and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate the weighted means and standard deviations for hip and knee kinematics (initial contact and peak values). 'Normal' motion was classified as the weighted mean plus/minus one standard deviation.

RESULTS

Of 2,920 citations, a total of 159 articles were identified as potentially relevant, with 29 meeting all inclusion/exclusion criteria. Due to the limited number of studies available examining double-leg drop landings and single-leg drop vertical jumps, insufficient data was available to include these tasks in the review. Therefore, a total of 25 articles were included. From the included studies, 'normal' ranges were calculated for the kinematic variables of interest across the athletic tasks examined.

LIMITATIONS

Joint forces and other additional elements play a role in ACL injuries, therefore, focusing solely on lower limb kinematics in classifying injury risk may not encapsulate all relevant factors. Insufficient data resulted in no normal ranges being calculated for double-leg drop land and single-leg drop vertical jump tasks. No included study examined hip internal/external rotation during single-leg drop landings, therefore ranges for this kinematic variable could not be determined. Variation in data between studies resulted in wide normal ranges being observed across certain kinematic variables.

CONCLUSIONS

The ranges calculated in this review provide evidence-based values that can be used to identify abnormal or anomalous athletic task performances on a multi-planar scale. This may be useful in identifying neuromuscular factors or specific muscular recruitment strategies that contribute to ACL injury risk.

Reproducibility measurements of three methods for calculating in vivo MR-based knee kinematics

PURPOSE

To describe three quantification methods for magnetic resonance imaging (MRI)-based knee kinematic evaluation and to report on the reproducibility of these algorithms.

MATERIALS AND METHODS

T2 -weighted, fast-spin echo images were obtained of the bilateral knees in six healthy volunteers. Scans were repeated for each knee after repositioning to evaluate protocol reproducibility. Semiautomatic segmentation defined regions of interest for the tibia and femur. The posterior femoral condyles and diaphyseal axes were defined using the previously defined tibia and femur. All segmentation was performed twice to evaluate segmentation reliability. Anterior tibial translation (ATT) and internal tibial rotation (ITR) were calculated using three methods: a tibial-based registration system, a combined tibiofemoral-based registration method with all manual segmentation, and a combined tibiofemoral-based registration method with automatic definition of condyles and axes. Intraclass correlation coefficients and standard deviations across multiple measures were determined.

RESULTS

Reproducibility of segmentation was excellent (ATT = 0.98; ITR = 0.99) for both combined methods. ATT and ITR measurements were also reproducible across multiple scans in the combined registration measurements with manual (ATT = 0.94; ITR = 0.94) or automatic (ATT = 0.95; ITR = 0.94) condyles and axes.

CONCLUSION

The combined tibiofemoral registration with automatic definition of the posterior femoral condyle and diaphyseal axes allows for improved knee kinematics quantification with excellent in vivo reproducibility.

Altered tibiofemoral kinematics in the affected knee and compensatory changes in the contralateral knee after anterior cruciate ligament reconstruction

BACKGROUND

Previous studies of knee kinematics after anterior cruciate ligament (ACL) reconstruction have generally employed low-effort tasks and typically not assessed changes in kinematics over time.

HYPOTHESES

(1) During single-legged hop landing, ACL-reconstructed limbs will have altered kinematics compared with contralateral (ACL-intact) limbs 5 months after surgery. (2) Kinematic differences between limbs will decrease over time because of changes in both ACL-reconstructed and ACL-intact limbs.

STUDY DESIGN

Controlled laboratory study.

METHODS

In vivo kinematics of ACL-reconstructed and contralateral ACL-intact knees were evaluated for 14 subjects during single-legged forward-hop landings at 5 and 12 months after surgery on the basis of dynamic stereo x-ray imaging. Differences between limbs and changes over time were assessed via repeated-measures analysis of variance.

RESULTS

Five months after surgery, ACL-reconstructed knees landed significantly less flexed compared with contralateral ACL-intact knees (20.9° vs 28.4°, respectively; P < .05). The ACL-reconstructed knees were significantly more externally rotated (12.2° vs 6.5°; P < .05) and medially translated (3.8 vs 2.3 mm; P < .009) compared with ACL-intact knees. Anterior-posterior translation was similar between limbs. From 5 to 12 months, knee flexion at landing increased in ACL-reconstructed knees (mean change, +3.4°; P < .05) and decreased in contralateral knees (mean change, -3.3°; P < .05). External tibial rotation also significantly decreased in ACL-reconstructed knees (-2.2°; P < .05) and increased in contralateral knees (+1.1°; P = .117) over time. Medial tibial translation decreased slightly over time only in ACL-reconstructed knees (-0.3 mm).

CONCLUSION

Five months after ACL reconstruction, landing kinematics differed between ACL-reconstructed and contralateral ACL-intact knees during a dynamic high-loading activity. These differences decreased over time, owing to changes in both the ACL-reconstructed and contralateral ACL-intact limbs.

CLINICAL RELEVANCE

This study identified kinematic changes over time in both the ACL-injured and contralateral ACL-intact knees after ACL reconstruction. These kinematic adaptations could have important implications for postoperative care, including evaluating the optimal timing of return to sports and the development of bilateral neuromuscular rehabilitation programs that may improve patient outcomes and reduce reinjuries in both the short and long terms.

A resistance band increased internal hip abduction moments and gluteus medius activation during pre-landing and early-landing

An increased knee abduction angle during jump-landing has been identified as a risk factor for anterior cruciate ligament injuries. Activation of the hip abductors may decrease the knee abduction angle during jump-landing. The purpose of this study was to examine the effects of a resistance band on the internal hip abduction moment and gluteus medius activation during the pre-landing (100ms before initial contact) and early-landing (100ms after initial contact) phases of a jump-landing-jump task. Thirteen male and 15 female recreational athletes (age: 21.1±2.4yr; mass: 73.8±14.6kg; height: 1.76±0.1m) participated in the study. Subjects performed jump-landing-jump tasks with or without a resistance band applied to their lower shanks. During the with-band condition, subjects were instructed to maintain their movement patterns as performing the jump-landing task without a resistance band. Lower extremity kinematics, kinetics, and gluteus medius electromyography (EMG) were collected. Applying the band increased the average hip abduction moment during pre-landing (p<0.001, Cohen׳s d (d)=2.8) and early-landing (p<0.001, d=1.5), and the average gluteus medius EMG during pre-landing (p<0.001, d=1.0) and early-landing (p=0.003, d=0.55). Applying the band decreased the initial hip flexion angle (p=0.028, d=0.25), initial hip abduction angle (p<0.001, d=0.91), maximum knee flexion angle (p=0.046, d=0.17), and jump height (p=0.004, d=0.16). Applying a resistance band provides a potential strategy to train the strength and muscle activation for the gluteus medius during jump-landing. Additional instructions and feedback regarding hip abduction, hip flexion, and knee flexion may be required to minimize negative changes to other kinematic variables.

Changes in landing mechanics in patients following anterior cruciate ligament reconstruction when wearing an extension constraint knee brace

BACKGROUND

Anterior cruciate ligament (ACL) reconstruction is associated with a high incidence of second tears (graft tears and contralateral ACL tears). These secondary tears have been attributed to asymmetrical lower extremity mechanics. Knee bracing is one potential intervention that can be used during rehabilitation that has the potential to normalize lower extremity asymmetry; however, little is known about the effect of bracing on movement asymmetry in patients following ACL reconstruction.

HYPOTHESIS

Wearing a knee brace would increase knee joint flexion and joint symmetry. It was also expected that the joint mechanics would become more symmetrical in the braced condition.

OBJECTIVE

To examine how knee bracing affects knee joint function and symmetry over the course of rehabilitation in patients 6 months following ACL reconstruction.

STUDY DESIGN

Controlled laboratory study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Twenty-three adolescent patients rehabilitating from ACL reconstruction surgery were recruited for the study. The subjects all underwent a motion analysis assessment during a stop-jump activity with and without a functional knee brace on the surgical side that resisted extension for 6 months following the ACL reconstruction surgery. Statistical analysis utilized a 2 × 2 (limb × brace) analysis of variance with a significant alpha level of 0.05.

RESULTS

Subjects had increased knee flexion on the surgical side when they were braced. The brace condition increased knee flexion velocity, decreased the initial knee flexion angle, and increased the ground reaction force and knee extension moment on both limbs. Side-to-side asymmetry was present across conditions for the vertical ground reaction force and knee extension moment.

CONCLUSION

Wearing a knee brace appears to increase lower extremity compliance and promotes normalized loading on the surgical side.

CLINICAL RELEVANCE

Knee extension constraint bracing in postoperative ACL patients may improve symmetry of lower extremity mechanics, which is potentially beneficial in progressing rehabilitation and reducing the incidence of second ACL tears.

Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing

ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the tensile stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps tensile stiffness would reduce peak anteromedial bundle (AM-)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive two-times body weight loads in compression, flexion, and internal tibial torque beginning at 15° flexion. Knees were equipped with modifiable custom springs to represent the nonlinear rapid stretch behavior of a normal and increased stiffness female quadriceps (i.e., 33% greater stiffness). Peak AM-ACL relative strain was measured using an in situ transducer while muscle forces and tibiofemoral kinematics and kinetics were recorded. A 3D ADAMS™ dynamic biomechanical knee model was used in silico to interpret the experimental results which were analyzed using a repeated-measures Wilcoxon test. Female knees exhibited a 16% reduction in peak AM-ACL relative strain and 21% reduction in change in flexion when quadriceps tensile stiffness was increased by 33% (mean (SD) difference: 0.97% (0.65%), p = 0.003). We conclude that increased quadriceps tensile stiffness reduces peak ACL strain during a controlled study simulating a pivot landing.

High body mass index is associated with increased diurnal strains in the articular cartilage of the knee

OBJECTIVE

Obesity is an important risk factor for osteoarthritis (OA) and is associated with changes in both the biomechanical and inflammatory environments within the joint. However, the relationship between obesity and cartilage deformation is not fully understood. The goal of this study was to determine the effects of body mass index (BMI) on the magnitude of diurnal cartilage strain in the knee.

METHODS

Three-dimensional maps of knee cartilage thickness were developed from 3T magnetic resonance images of the knees of asymptomatic age- and sex-matched subjects with normal BMI (18.5-24.9 kg/m2) or high BMI (25-31 kg/m2). Site-specific magnitudes of diurnal cartilage strain were determined using aligned images recorded at 8:00 AM and 4:00 PM on the same day.

RESULTS

Subjects with high BMI had significantly thicker cartilage on both the patella and femoral groove, as compared to subjects with normal BMI. Diurnal cartilage strains were dependent on location in the knee joint, as well as BMI. Subjects with high BMI, compared to those with normal BMI, exhibited significantly higher compressive strains in the tibial cartilage. Cartilage thickness on both femoral condyles decreased significantly from the AM to the PM time point; however, there was no significant effect of BMI on diurnal cartilage strain in the femur.

CONCLUSION

Increased BMI is associated with increased diurnal strains in articular cartilage of both the medial and lateral compartments of the knee. The increased cartilage strains observed in individuals with high BMI may, in part, explain the elevated risk of OA associated with obesity or may reflect alterations in the cartilage mechanical properties in subjects with high BMI.

The effects of femoral graft placement on cartilage thickness after anterior cruciate ligament reconstruction

Altered joint motion has been thought to be a contributing factor in the long-term development of osteoarthritis after ACL reconstruction. While many studies have quantified knee kinematics after ACL injury and reconstruction, there is limited in vivo data characterizing the effects of altered knee motion on cartilage thickness distributions. Thus, the objective of this study was to compare cartilage thickness distributions in two groups of patients with ACL reconstruction: one group in which subjects received a non-anatomic reconstruction that resulted in abnormal joint motion and another group in which subjects received an anatomically placed graft that more closely restored normal knee motion. Ten patients with anatomic graft placement (mean follow-up: 20 months) and 12 patients with non-anatomic graft placement (mean follow-up: 18 months) were scanned using high-resolution MR imaging. These images were used to generate 3D mesh models of both knees of each patient. The operative and contralateral knee models were registered to each other and a grid sampling system was used to make site-specific comparisons of cartilage thickness. Patients in the non-anatomic graft placement group demonstrated a significant decrease in cartilage thickness along the medial intercondylar notch in the operative knee relative to the intact knee (8%). In the anatomic graft placement group, no significant changes were observed. These findings suggest that restoring normal knee motion after ACL injury may help to slow the progression of degeneration. Therefore, graft placement may have important implications on the development of osteoarthritis after ACL reconstruction.

Estimation of tibiofemoral static zero position during dynamic drop landing

OBJECTIVE

The objective is to assess the in vivo knee secondary motions intrinsic to flexion in isolation from actual displacements during a landing activity. For this purpose a "static zero position", which denotes the normal tibiofemoral position to the static flexion angle, was introduced to describe the intrinsic secondary motion.

METHODS

The three-dimensional motion data of the healthy knee were collected from 13 male and 13 female young adults by using an auto motion analysis system and point cluster technique. First, the relationship between flexion and secondary motion in the static state was determined during a single-leg quasistatic squat. The static zero position during a single-leg drop landing was then calculated by substituting the flexion angle into the flexion-secondary relational expression obtained.

RESULTS

After the foot-ground contact, the estimated static zero positions shifted monotonically in valgus, internal rotation, and anterior translation in the case of both the male and female groups. For the time-course change, noticeable differences between the actual displacement and estimated static zero position were found from the foot-ground contact up to 25ms after the contact for the valgus/varus and external/internal rotation, and between 20 and 35ms after the contact for the anterior/posterior translation.

SUMMARY

The static zero position demonstrated relatively modest but not negligible shift in comparison with the actual displacement. The intrinsic tibiofemoral motion, or baseline shift, would be worth taking into account when examining the fundamental function and injury mechanics of the knee during an impulsive activity.

Combined in Vivo/in Vitro Method to Study Anteriomedial Bundle Strain in the Anterior Cruciate Ligament Using a Dynamic Knee Simulator

The mechanism of noncontact anterior cruciate ligament (ACL) injury is not well understood. It is partly because previous studies have been unable to relate dynamic knee muscle forces during sports activities such as landing from a jump to the strain in the ACL. We present a combined in vivo/in vitro method to relate the muscle group forces to ACL strain during jump-landing using a newly developed dynamic knee simulator. A dynamic knee simulator system was designed and developed to study the sagittal plane biomechanics of the knee. The simulator is computer controlled and uses six powerful electromechanical actuators to move a cadaver knee in the sagittal plane and to apply dynamic muscle forces at the insertion sites of the quadriceps, hamstring, and gastrocnemius muscle groups and the net moment at the hip joint. In order to demonstrate the capability of the simulator to simulate dynamic sports activities on cadaver knees, motion capture of a live subject landing from a jump on a force plate was performed. The kinematics and ground reaction force data obtained from the motion capture were input into a computer based musculoskeletal lower extremity model. From the model, the force-time profile of each muscle group across the knee during the movement was extracted, along with the motion profiles of the hip and ankle joints. This data was then programmed into the dynamic knee simulator system. Jump-landing was simulated on a cadaver knee successfully. Resulting strain in the ACL was measured using a differential variable reluctance transducer (DVRT). Our results show that the simulator has the capability to accurately simulate the dynamic sagittal plane motion and the dynamic muscle forces during jump-landing. The simulator has high repeatability. The ACL strain values agreed with the values reported in the literature. This combined in vivo/in vitro approach using this dynamic knee simulator system can be effectively used to study the relationship between sagittal plane muscle forces and ACL strain during dynamic activities.

High knee valgus in female subjects does not yield higher knee translations during drop landings: a biplane fluoroscopic study

The goal of this study was to determine the effects of peak knee valgus angle and peak knee abductor moment on the anterior, medial, and lateral tibial translations (ATT, MTT, LTT) in the "at risk" female knee during drop landing. Fifteen female subjects performed drop landings from 40 cm. Three-dimension knee motion was simultaneously recorded using a high speed, biplane fluoroscopy system, and a video-based motion analysis system. Valgus knee angles and knee abduction moments were stratified into low, intermediate, and high groups and peak ATT, MTT, and LTT were compared between these groups with ANOVA (α = 0.05). Significant differences were observed between stratified groups in peak knee valgus angle (p < 0.0001) and peak knee abduction moment (p < 0.0001). However, no corresponding differences in peak ATT, LTT, and MTT between groups exhibiting low to high-peak knee valgus angles (ATT: p = 0.80; LTT: p = 0.25; MTT: p = 0.72); or, in peak ATT (p = 0.61), LTT (p = 0.26) and MTT (p = 0.96) translations when stratified according to low to high knee abduction moments, were found. We conclude that the healthy female knee is tightly regulated with regard to translations even when motion analysis derived knee valgus angles and abduction moments are high.

Gender differences in landing mechanics vary depending on the type of landing

OBJECTIVE

Men and women exhibit different movement patterns, which are thought to contribute to the increased incidence of anterior cruciate ligament injuries in females. Although gender differences have been observed in movement, few studies have examined gender differences during different types of landings.

DESIGN

Prospective gender comparison study.

SETTING

Controlled laboratory study.

PATIENTS

Fourteen male and 14 female recreational soccer players were recruited for the study. All subjects performed a soccer-specific jump heading activity to examine differences in landing mechanics before and after heading the soccer ball. Subjects began the task by performing a forward jump onto 2 force platforms (landing 1) and conducting a countermovement before jumping up to head a soccer ball that was hanging above the force platform before, then landing back on the force platforms (landing 2).

MAIN OUTCOME MEASURES

A 2-way analysis of variance (gender × landing) was performed to examine the interaction between gender and different types of landings on sagittal plane joint mechanics.

RESULTS

Significant interactions existed for the peak hip extension moment and vertical ground reaction force where the male players exhibited increased values during the second landing compared with the female players. Males exhibited greater peak plantarflexion and knee extension moments, but decreased peak hip flexion. Main effects for landing exhibited lower kinematic and larger kinetic values except for the peak plantarflexion moment.

CONCLUSIONS

Female and male players appear to land differently depending on the type of landing. Therefore, specificity of landing type may be important to consider when screening for injury risk factors.

CLINICAL RELEVANCE

This study examines the differences between genders during 2 different landing tasks and demonstrates the importance of considering the jumping task when screening individuals for injury risk factors.

Prevention of ACL injury, part I: injury characteristics, risk factors, and loading mechanism

The anterior cruciate ligament (ACL) injury is one of the most common injuries in sports. ACL injuries are not only costly from financial and health services consumption standpoints, but also can have devastating consequences on patients' activity levels and quality of life. Tremendous efforts have been made over the past two decades toward the goal of preventing ACL injuries. A substantial number of studies have been performed to determine the characteristics of ACL injury events, identify risk factors for ACL injury, and develop prevention strategies. The purpose of this review was to objectively summarize the current literature regarding the characteristics of ACL injury, ACL loading mechanisms, and risk factors for injury to provide a comprehensive understanding of the current state of research and how our current level of knowledge may inform clinical practice in this area.

Anterior cruciate ligament reconstruction in adolescent patients: limb asymmetry and functional knee bracing

BACKGROUND

Anterior cruciate ligament (ACL) reinjury rates are high in adolescent patients. Knee braces are commonly used after ACL reconstruction to prevent reinjury during return to sports.

HYPOTHESIS

Adolescent patients following ACL injury would demonstrate a decreased vertical ground-reaction force, knee extension moment, knee flexion angle, and knee flexion velocity on the surgical limb when compared with the nonsurgical limb during a side-cutting task. A functional knee extension-resistant brace would decrease the limb asymmetries.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-three adolescent patients 6 months after ACL reconstruction were recruited for this study. Three-dimensional kinematic and kinetic data were collected bilaterally (surgical, nonsurgical) during a 35° side-cutting task while the patient was wearing and not wearing a functional knee extension-resistant brace (nonbraced, braced) on the surgical limb.

RESULTS

The surgical limb demonstrated a significant decrease in peak impact vertical ground-reaction force (2.55 body weight [BW] vs 2.8 BW; P < .01), peak propulsion vertical ground-reaction force (2.15 BW vs 2.3 BW; P < .01), peak knee extension moment (0.13 BW × body height [BH] vs 0.17 BW × BH; P < .01), knee flexion angle at peak knee flexion velocity (27.8° vs 30.0°; P = .01), peak knee flexion angle (44.1° vs 48.5°; P < .01), and peak knee flexion velocity (571.3 deg/sec vs 640.1 deg/sec; P < .01) when compared with the nonsurgical limb during both nonbraced and braced conditions. Bracing increased the initial knee flexion velocity (42.4 deg/sec vs -40.2 deg/sec; P = .01) and decreased the initial knee flexion angle on the surgical limb (13.1° vs 15.7°; P < .01). Bracing also affected kinematics of the nonsurgical limb. Bracing did not decrease the asymmetry between surgical and nonsurgical limbs.

CONCLUSION

Adolescent patients 6 months after ACL reconstruction demonstrated significant kinematic and kinetic asymmetries between the surgical and nonsurgical limbs. The limb asymmetries persisted when the patients were wearing a functional knee brace. There were changes in the surgical knee kinematics with and without bracing, especially near initial ground contact.

CLINICAL RELEVANCE

The limb asymmetries are of concern with regard to injuring the graft or the contralateral limb when the patients return to sport.

In vivo measurement of ACL length and relative strain during walking

Although numerous studies have addressed the effects of ACL injury and reconstruction on knee joint motion, there is currently little data available describing in vivo ACL strain during activities of daily living. Data describing in vivo ACL strain during activities such as gait is critical to understanding the biomechanical function of the ligament, and ultimately, to improving the surgical treatment of patients with ACL rupture. Thus, our objective was to characterize the relative strain in the ACL during both the stance and swing phases of normal level walking. Eight normal subjects were recruited for this study. Through a combination of magnetic resonance imaging, biplanar fluoroscopy, and motion capture, we created in vivo models of each subject's normal walking movements to measure knee flexion, ACL length, and relative ACL strain during gait. Regression analysis demonstrated an inverse relationship between knee flexion and ACL length (R(2)=0.61, p<0.001). Furthermore, relative strain in the ACL peaked at 13±2% (mean±95%CI) during mid-stance when the knee was near full extension. Additionally, there was a second local maximum of 10±7% near the end of swing phase, just prior to heel strike. These data are a vital step in further comprehending the normal in vivo biomechanics experienced by the ACL. In the future, this information could prove critical to improving ACL reconstruction and provide useful validation to future computational models investigating ACL function.

Diurnal variations in articular cartilage thickness and strain in the human knee

Due to the biphasic viscoelastic nature of cartilage, joint loading may result in deformations that require times on the order of hours to fully recover. Thus, cartilaginous tissues may exhibit cumulative strain over the course of each day. The goal of this study was to assess the magnitude and spatial distribution of strain in the articular cartilage of the knee with daily activity. Magnetic resonance (MR) images of 10 asymptomatic subjects (six males and four females) with mean age of 29 years were obtained at 8:00 AM and 4:00 PM on the same day using a 3T magnet. These images were used to create 3D models of the femur, tibia, and patella from which cartilage thickness distributions were quantified. Cartilage thickness generally decreased from AM to PM in all areas except the patellofemoral groove and was associated with significant compressive strains in the medial condyle and tibial plateau. From AM to PM, cartilage of the medial tibial plateau exhibited a compressive strain of -5.1±1.0% (mean±SEM) averaged over all locations, while strains in the lateral plateau were slightly lower (-3.1±0.6%). Femoral cartilage showed an average strain of -1.9±0.6%. The findings of this study show that human knee cartilage undergoes diurnal changes in strain that vary with site in the joint. Since abnormal joint loading can be detrimental to cartilage homeostasis, these data provide a baseline for future studies investigating the effects of altered biomechanics on diurnal cartilage strains and cartilage physiology.

Kinematic differences between optical motion capture and biplanar videoradiography during a jump-cut maneuver

Jumping and cutting activities are investigated in many laboratories attempting to better understand the biomechanics associated with non-contact ACL injury. Optical motion capture is widely used; however, it is subject to soft tissue artifact (STA). Biplanar videoradiography offers a unique approach to collecting skeletal motion without STA. The goal of this study was to compare how STA affects the six-degrees-of-freedom motion of the femur and tibia during a jump-cut maneuver associated with non-contact ACL injury. Ten volunteers performed a jump-cut maneuver while their landing leg was imaged using optical motion capture (OMC) and biplanar videoradiography. The within-bone motion differences were compared using anatomical coordinate systems for the femur and tibia, respectively. The knee joint kinematic measurements were compared during two periods: before and after ground contact. Over the entire activity, the within-bone motion differences between the two motion capture techniques were significantly lower for the tibia than the femur for two of the rotational axes (flexion/extension, internal/external) and the origin. The OMC and biplanar videoradiography knee joint kinematics were in best agreement before landing. Kinematic deviations between the two techniques increased significantly after contact. This study provides information on the kinematic discrepancies between OMC and biplanar videoradiography that can be used to optimize methods employing both technologies for studying dynamic in vivo knee kinematics and kinetics during a jump-cut maneuver.

The effect of modified Broström-Gould repair for lateral ankle instability on in vivo tibiotalar kinematics

BACKGROUND

Lateral ankle instability leads to an increased risk of tibiotalar joint osteoarthritis. Previous studies have found abnormal tibiotalar joint motions with lateral ankle instability that may contribute to this increased incidence of osteoarthritis, including increased anterior translation and internal rotation of the talus under weightbearing loading. Surgical repairs for lateral ankle instability have shown good clinical results, but the effects of repair on in vivo ankle motion are not well understood.

HYPOTHESIS

The modified Broström-Gould lateral ligament reconstruction decreases anterior translation and internal rotation of the talus under in vivo weightbearing loading conditions.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven patients underwent modified Broström-Gould repair for unilateral lateral ankle instability. Ankle joint kinematics as a function of increasing body weight was studied with magnetic resonance imaging and biplanar fluoroscopy. Tibiotalar kinematics was measured in unstable ankles preoperatively and postoperatively at a mean follow-up of 12 months as well as in the uninjured contralateral ankles of the same patients.

RESULTS

Surgical repair resulted in statistically significant decreases (expressed as mean ± standard error of the mean) in anterior translation of the talus (0.9 ± 0.3 mm; P = .018) at 100% body weight and internal rotation of the talus at 75% (2.6° ± 0.8°; P = .019) and 100% (2.7° ± 0.8°; P = .013) body weight compared with ankle kinematics measured before repair. No statistically significant differences were detected between repaired ankles and contralateral normal ankles.

CONCLUSION

The modified Broström-Gould repair improved the abnormal joint motion observed in patients with lateral ankle instability, decreasing anterior translation and internal rotation of the talus.

CLINICAL RELEVANCE

Altered kinematics may contribute to the tibiotalar joint degeneration that occurs with chronic lateral ankle instability. The findings of the current study support the efficacy of this repair in improving the abnormal ankle motion observed in these patients.

The effects of a valgus collapse knee position on in vivo ACL elongation

There are conflicting data regarding what motions increase ACL injury risk. More specifically, the mechanical role of valgus collapse positions during ACL injury remains controversial. Our objective was to evaluate ACL elongation in a model that mimics knee movements thought to occur during ACL injury. Eight healthy male subjects were imaged using MR and biplanar fluoroscopy to measure the in vivo elongation of the ACL and its functional bundles during three static knee positions: full extension, 30° of flexion, and a position intended to mimic a valgus collapse position described in the literature. For this study, the valgus collapse position consisted of 30° of knee flexion, internal rotation of the hip, and 10° of external tibial rotation. ACL length decreased significantly from full extension (30.2 ± 2.6 mm) to 30° of flexion (27.1 ± 2.2 mm). ACL length further decreased in the valgus collapse position (25.6 ± 2.4 mm). Both functional bundles of the ACL followed similar trends with regards to decreases in length in each of the three positions. Since strain would follow patterns of ACL length, landing on an extended knee may be a more relevant risk factor for ACL injuries than the valgus collapse position in males. Future studies should evaluate the effects of dynamic motion patterns on in vivo ACL strains.

Static and dynamic error of a biplanar videoradiography system using marker-based and markerless tracking techniques

The use of biplanar videoradiography technology has become increasingly popular for evaluating joint function in vivo. Two fundamentally different methods are currently employed to reconstruct 3D bone motions captured using this technology. Marker-based tracking requires at least three radio-opaque markers to be implanted in the bone of interest. Markerless tracking makes use of algorithms designed to match 3D bone shapes to biplanar videoradiography data. In order to reliably quantify in vivo bone motion, the systematic error of these tracking techniques should be evaluated. Herein, we present new markerless tracking software that makes use of modern GPU technology, describe a versatile method for quantifying the systematic error of a biplanar videoradiography motion capture system using independent gold standard instrumentation, and evaluate the systematic error of the W.M. Keck XROMM Facility's biplanar videoradiography system using both marker-based and markerless tracking algorithms under static and dynamic motion conditions. A polycarbonate flag embedded with 12 radio-opaque markers was used to evaluate the systematic error of the marker-based tracking algorithm. Three human cadaveric bones (distal femur, distal radius, and distal ulna) were used to evaluate the systematic error of the markerless tracking algorithm. The systematic error was evaluated by comparing motions to independent gold standard instrumentation. Static motions were compared to high accuracy linear and rotary stages while dynamic motions were compared to a high accuracy angular displacement transducer. Marker-based tracking was shown to effectively track motion to within 0.1 mm and 0.1 deg under static and dynamic conditions. Furthermore, the presented results indicate that markerless tracking can be used to effectively track rapid bone motions to within 0.15 deg for the distal aspects of the femur, radius, and ulna. Both marker-based and markerless tracking techniques were in excellent agreement with the gold standard instrumentation for both static and dynamic testing protocols. Future research will employ these techniques to quantify in vivo joint motion for high-speed upper and lower extremity impacts such as jumping, landing, and hammering.

Automated measurement of neural foramen cross-sectional area during in vivo functional movement

An automated technique to measure neural foramen cross-sectional area during in vivo, multi-planar movements is presented. This method combines three-dimensional (3D) models of each vertebra obtained from CT scans with in vivo movement data collected using high-speed biplane radiography. A novel computer algorithm that automatically traces a path around the bony boundary that defines the neural foramen at every frame of X-ray data is described. After identifying the neural foramen boundary, the cross-sectional area is calculated. The technique is demonstrated using data collected from a patient with cervical radiculopathy who is tested before and after conservative treatment. The technique presented here can be applied when 3D, dynamic, functional movements are performed. Neural foramen cross-sectional area can be quantified at specific angles of intervertebral rotation, allowing for matched comparisons between two trials or two test sessions. The present technique is ideal for longitudinal studies involving subjects who receive conservative or surgical treatments that may affect spine motion.

Tibio-femoral joint constraints for bone pose estimation during movement using multi-body optimization

When using skin markers and stereophotogrammetry for movement analysis, bone pose estimation may be performed using multi-body optimization with the intent of reducing the effect of soft tissue artefacts. When the joint of interest is the knee, improvement of this approach requires defining subject-specific relevant kinematic constraints. The aim of this work was to provide these constraints in the form of plausible values for the distances between origin and insertion of the main ligaments (ligament lengths), during loaded healthy knee flexion, taking into account the indeterminacies associated with landmark identification during anatomical calibration. Ligament attachment sites were identified through virtual palpation on digital bone templates. Attachments sites were estimated for six knee specimens by matching the femur and tibia templates to low-dose stereoradiography images. Movement data were obtained using stereophotogrammetry and pin markers. Relevant ligament lengths for the anterior and posterior cruciate, lateral collateral, and deep and superficial bundles of the medial collateral ligaments (ACL, PCL, LCL, MCLdeep, MCLsup) were calculated. The effect of landmark identification variability was evaluated performing a Monte Carlo simulation on the coordinates of the origin-insertion centroids. The ACL and LCL lengths were found to decrease, and the MCLdeep length to increase significantly during flexion, while variations in PCL and MCLsup length was concealed by the experimental indeterminacy. An analytical model is given that provides subject-specific plausible ligament length variations as functions of the knee flexion angle and that can be incorporated in a multi-body optimization procedure.