Experimental analysis of the quadriceps muscle force and patello-femoral joint reaction force for various activities

How isometric are the medial patellofemoral, superficial medial collateral, and lateral collateral ligaments of the knee?

BACKGROUND

Ligament isometry is a cornerstone in the description of normal knee function and thorough knowledge is mandatory for successful repair of torn ligaments.

PURPOSE

This study was undertaken to validate a novel experimental model for the study of ligament strains and to determine the length changes in the superficial medial collateral, lateral collateral, and medial patellofemoral ligaments.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Passive motions and loaded squats of 12 cadaveric specimens were performed while controlling ankle load and optically tracking the motion of the bones. Preexperiment and postexperiment computed axial tomography scans allow the transformation of rigid body motion to relative motion of relevant anatomic landmarks on the femur, tibia, and patella.

RESULTS

The superficial medial collateral ligament is a near-isometric ligament with a strain of less than 2%. The ligament is a little more slack in midflexion (30 degrees to 50 degrees ) and in deep flexion, but length changes are not significant (P > .05). The lateral collateral ligament behaves near isometric (<2% strain) from 0 degrees to 70 degrees of knee flexion. Cartilage compression in a loaded environment relieves tension from the collateral ligaments (P < .05). The medial patellofemoral ligament is nonisometric. The cranial part of the medial patellofemoral ligament is most taut at full extension, while the caudal part is most taut at 30 degrees of knee flexion.

CONCLUSION

Ligament insertion sites on the femur, patella, and fibula can be derived from computed axial tomography scans. The described model allows the study of dynamic ligament behavior. The superficial medial collateral ligament is a near-isometric ligament with no significant length changes. The medial patellofemoral ligament behaves differently in its cranial and caudal parts.

CLINICAL RELEVANCE

In knees with chronic medial collateral ligament insufficiency, isometric repair of the superficial medial collateral ligament can be attempted. A medial patellofemoral ligament reconstruction with a double fixation on the medial patellar border is supported. The cranial bundle should be tightened at full extension and the caudal bundle at 30 degrees of knee flexion.

The effect of patellar taping on joint reaction forces during squatting in subjects with Patellofemoral Pain Syndrome (PFPS)

SUMMARY INTRODUCTION

The mechanisms of pain reduction have not completely been established following patellar taping in subjects with patellofemoral pain syndrome (PFPS); although it might be related to alteration in the kinetics of the patellofemoral joint.

METHODS

Patellofemoral Joint Reaction Force (PFJRF) of eighteen subjects with PFPS and eighteen healthy subjects as controls were assessed by a motion-analysis system and one force plate. This procedure was performed on the affected knee of subjects with PFPS, before, during and finally after patellar taping during unilateral squatting. A similar procedure was also performed on the unaffected knees of both groups.

RESULTS

The mean values of PFJRF prior to taping (2025N, SD 347N) were decreased significantly following a period of taping (1720N, SD 303N) (P<0.05). There were no significant differences between the mean values of PFJRF among controls (1922N, SD 398N) and subjects with PFPS prior to taping (P>0.05) which might be due to small sample size in both groups and large variability observed in the study.

INTERPRETATION

Decreased values of PFJRF may explain the mechanism of pain reduction following patellar taping in subjects with PFPS.

Iliotibial band release as an adjunct to the surgical management of patellar stress fracture in the athlete: a case report and review of the literature

Stress fracture of the patella is rare. In this report, a case of patellar stress fracture occurring in an amateur athlete is presented, and an operative adjunct to the surgical management of this condition is proposed.

A review of the English literature identified 21 previous cases of stress fracture of the patella, the majority in young athletes. None of these reports discussed treatment addressing the pathological process contributing to patellar stress fracture.

The subject of this case report is a young male netballer who presented with a transverse stress fracture in the inferior third of his patella, on a background of patellofemoral overload. The patient underwent open reduction and internal fixation of his patella, combined with release of the iliotibial band. He returned to training after 6 weeks.

The previous literature suggests that operative fixation is indicated for the treatment of displaced patellar stress fractures. Iliotibial band release, as a surgical adjunct to this treatment, may address the pathology of these fractures, and facilitate a return to sport at the highest level.

[Biomechanical issues in patellofemoral joint rehabilitation]

Specific knowledge of the biomechanics of the patellofemoral joint is crucial for successful nonoperative or postsurgical rehabilitation. The biomechanical aspects of different situations should be considered when designing an exercise program. Joint reaction forces, contact area, and contact stress are dependent on flexion angle and exercise situations. In weight-bearing activities, the amount of knee flexion directly influences the magnitude of quadriceps muscle force, which affects the magnitude of patellofemoral joint reaction forces. Open and closed chain exercises should be performed within a safe range of motion to allow quadriceps activation while minimizing patellofemoral joint reaction forces. The isolated knee extension (90 degrees -40 degrees ), the squat (0 degrees -30 degrees -60 degrees ), and the leg press (0 degrees -30 degrees -60 degrees ) are the three main exercise situations in the acute rehabilitation phase. Controlled body positions and low levels of pain and symptoms should also be emphasized to achieve a functional progression, focusing on neuromuscular control.

Patellofemoral joint forces

In this review of patellofemoral joint forces as they might apply to implant design, methodologies for estimating forces on the patella and estimates of the forces, as reported in the literature, are summarized. Two methodologies exist for studying joint loads; one that measures kinematics in-vivo and uses analysis to estimate the joint loads and another that measures ground reaction forces and uses analysis to estimate the joint loads. In both these analyses many assumptions are required with varying degrees of uncertainty; here, those assumptions are examined with data from the published literature. The topics covered include: relationships between quadriceps forces and patellofemoral forces or patella ligament forces, relationships between knee joint moments and quadriceps forces, knee joint moments in various gaits, relationships between patellofemoral forces and lateral subluxation forces, and relationships between patella forces and inferior-superior forces. In many cases, there is little data on patella forces during normal activities, in other cases, there are some discrepancies in reported patella forces, i.e. during squat.

Joint Loading in the Lower Extremities during Elliptical Exercise

PURPOSE

To determine the joint loading during elliptical exercise (EE) by a detailed three-dimensional dynamic analysis, and to compare the results with those during level walking.

METHODS

Fifteen male adults performed level walking and EE while 3D kinematic data, right pedal reaction forces (PRF), and ground reaction forces (GRF) were measured. Pedal rate (cadence) and step length during EE without workload were set according to those measured during level walking for each subject. The motion of the body's center of mass, lower-limb-joint angles and moments were obtained.

RESULTS

Pedal rates and step lengths were 52.20 rpm (SD=2.34) and 50.56 cm (SD=2.14), respectively. During early stance the vertical PRF was smaller than the GRF, and the medial and posterior shear components were greater. PRF also occurred during swing. Loading rates around heelstrike during EE were all smaller than those during walking. During EE, the peak flexion angles of the hip, knee and ankle were greater. Peak hip flexor and knee extensor moments were also greater, whereas peak ankle plantarflexor moments and all abductor moments were smaller.

CONCLUSIONS

Different lower-limb kinematics and kinetics were found between EE and level walking. Smaller vertical PRF and loading rates during EE were achieved at the expense of greater hip flexor and knee extensor moments. Use of the elliptical trainer for athletic and rehabilitative training would have to consider users' joint function and muscle strength, especially at the knee, to avoid injuries.

Avaliação quantitativa das forças laterais da patela: ressonância magnética estática e cinemática

OBJETIVO: Avaliar a validade da ressonância magnética cinemática combinada com a ressonância magnética estática no estudo da articulação femoropatelar. MATERIAIS E MÉTODOS: Foram realizadas ressonância magnética estática e ressonância magnética cinemática em 20 voluntários assintomáticos (40 joelhos) e em 23 pacientes (43 joelhos), em aparelho de configuração fechada de 1,5 tesla de campo. Os indivíduos foram posicionados na extremidade da mesa, em 30° de flexão. A translação patelar foi avaliada medindo-se o desvio da bissetriz, o deslocamento lateral da patela e o ângulo de inclinação da patela. Para a comparação entre os estudos estático e cinemático, foi utilizado o teste não-paramétrico de Wilcoxon. Para a comparação entre os voluntários e os pacientes, foi utilizado o teste de Mann-Whitney. RESULTADOS: Houve diferenças significantes entre a ressonância magnética estática e a ressonância magnética cinemática (p < 0,05) nos três parâmetros utilizados. No grupo dos pacientes, as diferenças entre a ressonância magnética estática e a ressonância magnética cinemática foram maiores que nos voluntários a 20° e a 30° de flexão, com o desvio da bissetriz e com o deslocamento lateral da patela. CONCLUSÃO: A combinação da ressonância magnética estática e ressonância magnética cinemática evidenciou que a força resultante lateral é maior na faixa de 20° e 30° de flexão, especialmente nos indivíduos sintomáticos, para a instabilidade femoropatelar.

Review for the generalist: evaluation of anterior knee pain

Anterior knee pain is common in children and adolescents. Evaluation and management is challenging and requires a thorough history and physical exam, and understanding of the pediatric skeleton. This article will review common causes of chronic anterior knee pain in the pediatric population with a focus on patellofemoral pain.

Dynamic measurement of patellofemoral kinematics and contact pressure after lateral retinacular release: an in vitro study

The purpose of this study was to investigate the influence of lateral retinacular release and medial and lateral retinacular deficiency on patellofemoral position and retropatellar contact pressure. Human knee specimens (n = 8, mean age = 65 SD 7 years, all male) were tested in a kinematic knee-simulating machine. During simulation of an isokinetic knee extension cycle from 120 degrees to full extension, a hydraulic cylinder applied sufficient force to the quadriceps tendon to produce an extension moment of 31 Nm. The position of the patella was measured using an ultrasound based motion analysis system (CMS 100, Zebris). The amount of patellofemoral contact pressure and its pressure distribution was measured using a pressure sensitive film (Tekscan, Boston). Patellar position and contact pressure were first investigated in intact knee conditions, after a lateral retinacular release and a release of the medial and lateral retinaculum. After lateral retinacular release the patella continuously moved from a significant medialised position at flexion (P = 0.01) to a lateralised position (P = 0.02) at full knee extension compared to intact conditions, the centre of patellofemoral contact pressure was significantly medialised (0.04) between 120 degrees and 60 degrees knee flexion. Patellofemoral contact pressure did not change significantly. In the deficient knee conditions the patella moved on a significant lateralised track (P = 0.04) through the entire extension cycle with a lateralised centre of patellofemoral pressure (P = 0.04) with a trend (P = 0.08) towards increased patellofemoral pressure. The results suggest that lateral retinacular release did not inevitably stabilise or medialise patellar tracking through the entire knee extension cycle, but could decrease pressure on the lateral patellar facet in knee flexion. Therefore lateral retinacular release should be considered carefully in cases of patellar instability.

In vitro measurement of patellar kinematics following reconstruction of the medial patellofemoral ligament

This study compares the effects of two different techniques of medial patellofemoral ligament (MPFL) reconstruction, and proximal soft tissue realignment on patellar stabilization against lateral dislocation. Eight human cadaver knee specimens with no radiological pathomorpholgy on a straight lateral view, contributing to patellofemoral instability, were mounted in a kinematic knee simulator and isokinetic extension was simulated. Patellar kinematics were measured with an ultrasound positioning system (zebris) while a 100 N laterally directed force was applied to the patella. The kinematics were compared with intact knee conditions under MPFL deficient conditions, as well as following dynamic reconstruction of the MPFL using a distal transfer of the semitendinosus tendon, following static reconstruction by a semitendinosus autograft, and following proximal soft tissue realignment of the patella (Insall procedure). Dynamic reconstruction of the MPFL resulted in no significant alteration (P = 0.16) of patellar kinematics. Static reconstruction of the MPFL significantly medialized (P < 0.01) the patellar movement without, but restored intact knee kinematics under the laterally directed force. In contrast, following proximal soft tissue realignment, the patellar movement was constantly medialized and internally tilted (P = 0.04). Dynamic and static reconstruction of the MPFL create sufficient stabilization of the patella. Following proximal soft tissue realignment, the patellar position was over-medialized relative to intact knee conditions, which could lead to an overuse of the medial retropatellar cartilage.

Dynamic measurement of patellofemoral contact pressure following reconstruction of the medial patellofemoral ligament: an in vitro study

BACKGROUND

Surgical reconstruction of the medial patellofemoral ligament used to stabilize the patella against lateral dislocation may concomitantly produce alteration of the patellofemoral contact pressure distribution. Two different tendon transfer techniques of reconstructing the medial patellofemoral ligament, one dynamic and one static, as well as a proximal soft tissue realignment of the patella were investigated.

METHODS

Eight human knee specimens were mounted in a kinematic knee simulator and isokinetic extension motion was simulated. Patellofemoral pressure was measured using a pressure sensitive film while a 100 N laterally directed dislocation load was applied to the patella. The specimens were evaluated in a physiologic state, as well as after dynamic reconstruction of the medial patellofemoral ligament using a distal transfer of the semitendinosus tendon, following static reconstruction using a semitendinosus autograft, and following proximal soft tissue realignment of the patella.

FINDINGS

Following both reconstruction techniques of the medial patellofemoral ligament patellofemoral contact pressure was not significantly (P=0.49) altered. In contrast, after proximal realignment a trend (P=0.07) towards higher contact pressure near knee extension was observed. In the absence of a lateral dislocation load dynamic and static reconstruction resulted in a medialization (P=0.04) of the center of pressure, whereas under the application of a 100 N dislocation load the center of pressure showed no significant alteration. Following proximal realignment the center of pressure was significantly medialized without (P<0.01) and with a dislocation load (P=0.01) throughout the entire range of knee motion.

INTERPRETATION

Static and dynamic ligament reconstruction of the medial patellofemoral ligament did not alter patellofemoral pressure. Proximal realignment, on the other hand, resulted in a constant medialization of the patellofemoral pressure. The data suggest that the reconstruction techniques would be associated with a low risk of causing premature cartilage degeneration due to excessive patellofemoral contact pressure, whereas proximal realignment could cause medial overload of the patellofemoral joint.

Knee angular impulse as a predictor of patellofemoral pain in runners

BACKGROUND

Identification of mechanical factors associated with patellofemoral pain, the most prevalent running injury, is necessary to help in injury prevention, but unfortunately they remain elusive.

HYPOTHESIS

Runners who develop patellofemoral pain have increased knee joint angular impulse in the frontal plane.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

A retrospective study compared knee abduction impulses of 20 patellofemoral pain patients with those of 20 asymptomatic patients. A second prospective study quantified knee angular impulses during the stance phase of running of 80 runners at the beginning of the summer running season. Epidemiologic data were then collected, recording the type and severity of injury of these runners during a 6-month running period.

RESULTS

The patellofemoral pain patients in the retrospective study had significantly higher (P = .026) knee abduction impulses (17.0 +/- 8.5 Nms) than did the asymptomatic patients (12.5 +/- 5.5 Nms). Six patients developed patellofemoral pain during the prospective study. The prospective data showed that patients who developed patellofemoral pain had significantly higher (P = .042) knee abduction impulses (9.2 +/- 3.7 Nms) than did matched patients who remained uninjured (4.7 +/- 3.5 Nms).

CONCLUSION

The data indicate that increased knee abduction impulses should be deemed risk factors that play a role in the development of patellofemoral pain in runners.

CLINICAL RELEVANCE

Footwear and running style can influence knee angular impulse, and the appropriate manipulation of these variables may play a preventive role for patients who are predisposed to patellofemoral pain.

A 12-28-year followup study of closing wedge high tibial osteotomy

Current indications for high tibial osteotomy (HTO) are controversial although several risk factors have been associated with HTO survival. We ascertained the influence of preoperative variables in a consecutive series of patients who had closing wedge HTO at a minimum of 12 year followup (mean 18-year, range 12 to 28 years). Three hundred one of an initial 372 high tibial osteotomies (313 patients) were included (81% followup); 71 knees were eliminated because patients died (30 knees) or were lost to followup (41 knees). The mean age was 42 years (range, 15-76 years), 194 were men and 119 were women. The osteotomy was fixed by a Blount staple and an AO half-tube plate with three screws. Forty-three knees (14%) in 39 patients were revised for progression of osteoarthritis at an average of 102 months. Survival was 85% at 20 years with revision as the endpoint. Knee function was considered satisfactory by 77% of patients. At final followup, 1/2 of the knees showed radiographic signs of medial osteoarthritis. The most important risk factors predicting revision were age greater than 50 years and a preoperative arthritis Ahlback grade of 3 or more.

Structural parameters of the vastus medialis muscle and its relationship to patellofemoral joint deterioration

Vastus medialis (VM) muscle dysfunction and abnormal limb alignment are commonly observed in patients who experience changes in patellofemoral joint (PFJ) function, leading many clinicians to assume that there is a direct relationship between VM structural parameters, leg alignment, and PFJ dysfunction. This study tested the hypothesis that there is a relationship between structural parameters of the VM muscle, limb alignment, and the location and severity of patellofemoral joint deterioration (PFJD). The dissection study used 32 limbs from 24 intact cadavers. Data were collected on limb alignment, angle of VM muscle fibers below the superior aspect of the patella, length of VM inserting on the medial aspect of the patella, and severity and location of PFJD. Parametric and nonparametric statistical analyses illustrated that PFJD was most commonly located on the middle third of the medial half of the patellar articular surface. The severity of PFJD did not vary with location. There was no significant correlation between any of VM insertion length, VM fiber angle, limb alignment, and PFJD location and severity lpar;r(2) < 0.34). The results of this study did not support the hypothesis of a relationship between structural parameters of the VM muscle, limb alignment, and the location and severity of PFJD in this subject group. Future research should examine the relationship between functional parameters of the entire quadriceps muscle group and PFJ dysfunction.

Reliability of a technique for determining sagittal knee geometry from lateral knee radiographs

The purposes of this study were to describe an analytical technique for determining selected 2-dimensional geometric characteristics of a knee joint using lateral knee radiographs and to examine the inter- and intra-analyst reliability of this technique. Five lateral knee radiographs of different knee flexion angles (25-85 degrees at intervals of 15 degrees ) were obtained from five subjects. Two graduate and five undergraduate students with knowledge of knee anatomy served as the analysts and were asked to identify certain landmarks from the radiographs. The coordinates of these landmarks were used to determine the effective moment arm of the quadriceps force, patellar tendon length, patella height, patellar mechanism and patellar tendon angles, and tibiofemoral and patellofemoral joint spaces. For each radiograph, intraclass correlation coefficients (ICCs) were computed for combinations of 2-7 analysts. Using all seven analysts, the ICCs ranged from 0.9967 to 0.9985 for different radiographs. When fewer analysts were used, the average ICCs were 0.9975 (6 analysts), 0.9974 (5 analysts), 0.9974 (4 analysts), 0.9974 (3 analysts), and 0.9973 (2 analysts). Four of the analysts re-analyzed the radiographs 2-3months after the initial analyses. Intra-analyst ICCs ranged from 0.9842 to 0.9999. Overall, the high ICC values indicate excellent inter- and intra-analyst reliability. The proposed technique is reliable and may be used for both clinical and research purposes. The relatively small reductions in ICCs when fewer analysts were used suggest that a single experienced analyst is sufficient for clinical assessment. However, 2-3 analysts are recommended for research purposes.

Periprosthetic patellar fractures

Patellar fracture after total knee arthroplasty is a rare yet challenging complication. Patellar fracture can occur as a result of trauma or it may be atraumatic. A multitude of factors can lead to periprosthetic patellar fracture including patient related factors, surgical technique related factors, and implant specific factors. Understanding the etiologic factors leading to atraumatic patellar fractures could result in minimizing complications. We present the results of peri-prosthetic patellar fractures in 12 patients. All type I non-displaced fractures (7 cases) were treated nonoperatively. Surgical treatment was selected for the remaining 5 cases which included resection arthroplasty combined with open reduction and internal fixation of the fracture (3 knees), partial patellectomy (1 knee), and total patellectomy (1 knee). The outcome was excellent in 1 knee, good in 8 knees, and fair in the remaining 3 knees at the latest follow-up. There were 2 reoperations; 1 for disruption of the extensor mechanism and 1 for refracture. One patient developed a superficial wound infection. We reviewed the available literature regarding the etiology, surgical strategies, and outcomes for periprosthetic patellar fracture.

LEVEL OF EVIDENCE

Therapeutic studies, level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

In vitro investigation of the effect of medial patellofemoral ligament reconstruction and medial tibial tuberosity transfer on lateral patellar stability

PURPOSE

Two different operative techniques for stabilizing the patella against lateral displacement movement were investigated.

TYPE OF STUDY

In vitro experimental study.

METHODS

Five human cadaver knee specimens with a normal Q-angle were mounted in a kinematic knee simulator and investigated under simulated isokinetic extension motions. Patellar movement was measured while a 100-N laterally directed subluxation load was applied to the patella. Ligament loading of the medial patellofemoral ligament was measured using a strain gauge based buckle transducer inserted in the fibers of the ligament. The knee was evaluated in an intact physiologic state, as well as after medial transfer of the tibial tuberosity, and after the medial patellofemoral ligament was transected and reconstructed using a hamstring autograft.

RESULTS

A significant reduction in lateral displacement and ligament load was observed with the use of the hamstring autograft reconstruction compared with the medial transfer of the tibial tuberosity.

CONCLUSIONS

Medial transfer of the tibial tuberosity showed no significant relief of ligament loading and stabilizing effect on patellar movement, whereas reconstruction of the medial patellofemoral ligament showed a significant stabilizing effect on patellar movement.

CLINICAL RELEVANCE

In cadaver specimens, we evaluated the effect of tibial tubercle transfer and the patellofemoral ligament and found that reconstruction of the patellofemoral ligament alone was sufficient to restore stability in a cadaveric model. Additionally, we found that the flexion angle had little effect on the loading of the medial patellofemoral ligament autograft, which would support early mobilization of patients after surgery. We found that the graft was not unduly loaded.

Stress Fractures Around the Knee

Stress fractures of the lower extremities are common, especially in the younger athletic population. The current literature consists mainly a variety of case reports but is devoid of any sizeable series of knee stress fracture investigations. Diagnosing a stress fracture around the knee can be a challenge. The proximity of the stress fracture to the knee joint may lead the clinician to investigate intra-articular or other periarticular pathology. The differential diagnosis can be large, including bursitis, tendonitis, mechanical causes, insufficiency fracture, and tumor. A high index of suspicion is necessary to confirm the underlying diagnosis. A patient's medical history combined with a physical examination and imaging modalities will aid the physician in arriving at the diagnosis of stress fracture.

Pathologic patellar fracture at the site of an old Sinding-Larsen-Johansson lesion: a case report of a 33-year-old male

A Sinding-Larsen-Johansson lesion is considered to be a self-limited process. Delayed sequelae of this disease have not previously been discussed. We present a case of a pathologic patellar fracture through a site of an old Sinding-Larsen-Johansson lesion.

Complete rupture of large tendons: risk factors, signs, and definitive treatment

Forceful eccentric contraction may cause a partial or complete rupture of a vulnerable large tendon, especially in middle-aged men. When diagnosing a large-tendon rupture, it is essential to rule out a systemic illness or history of local or systemic corticosteroid or anabolic steroid use, because any of these may lead to poor tendon quality and increased risk for rupture. Ultrasound or MRI may help confirm the diagnosis. Treatment is generally surgical with anatomic repair. Return to sport depends on the patient's age, lifestyle, tendon involved, and medical comorbidities.

Patellofemoral pain syndrome: evaluation and treatment

Patellofemoral pain syndrome is common among athletes and non-athletes. It results from an imbalance of forces acting on the patellofemoral joint, which leads to increased strain on the peripatellar soft tissues, increased patellofemoral joint stress, or both. The most important risk factors are overuse, quadriceps weakness, and soft-tissue tightness. In most cases, the etiology is multifactorial. A careful history and targeted physical examination will confirm the diagnosis and determine the most appropriate treatment. A physical therapy program that employs quadriceps strengthening, manual stretching of the lateral patellar soft-tissue structures, patellar taping, and biofeedback is successful in the majority of cases. Surgery maybe required for the few patients who do not respond to nonoperative management.

Moderate-Heeled Shoes and Knee Joint Torques Relevant to the Development and Progression of Knee Osteoarthritis

OBJECTIVE

To determine if women's dress shoes with heels of just 1.5 in (3.8 cm) in height increases knee joint torques, which are thought to be relevant to the development and/or progression of knee osteoarthritis (OA) in both the medial and patellofemoral compartments.

DESIGN

Randomized controlled trial.

SETTING

A 3-dimensional motion analysis gait laboratory.

PARTICIPANTS

Twenty-nine healthy young women (age, 26.7+/-5.0 y) and 20 healthy elderly adult women (age, 75.3+/-6.5 y).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Peak external varus knee torque in early and late stance and prolongation of flexor knee torque in early stance. Three-dimensional data on lower-extremity torques and motion were collected during walking while (1) wearing shoes with 1.5-in high heels and (2) wearing control shoes without any additional heel. Data were plotted and qualitatively compared; major peak values and timing were statistically compared between the 2 conditions using paired t tests.

RESULTS

Peak knee varus torque during late stance was statistically significantly greater with the heeled shoes than with the controls, with increases of 14% in the young women and 9% in the elderly women. With the heeled shoes, the early stance phase knee flexor torque was significantly prolonged, by 19% in the young women and by 14% in elderly women. Also, the peak flexor torque was 7% higher with the heeled shoe in the elderly women.

CONCLUSIONS

Even shoes with moderately high heels (1.5 in) significantly increase knee torques thought to be relevant in the development and/or progression of knee OA. Women, particularly those who already have knee OA, should be advised against wearing these types of shoes.

The influence of tibial and femoral rotation on patellofemoral contact area and pressure

Fixed rotation of either the femur or tibia has a significant influence on the patellofemoral joint contact areas and pressures. This is due to the anatomic asymmetry in the knee with respect to all planes, as well as the laterally directed force vector that naturally exists in bipedal lower-limb biomechanics. Specifically, femoral rotation results in an increase in patellofemoral contact pressures on the contralateral facets of the patella, and tibial rotation results in an increase in patellofemoral contact pressures on the ipsilateral facets of the patella. This difference can be elucidated when one considers that rotation of the femur is biomechanically different than rotation of the tibia. For both tibial and femoral rotations, the patella's distal attachment to the tibial tubercle influences the direction of patellar movement. The biomechanical evidence reviewed in this manuscript suggests that the determining factor in patellofemoral pathology is the derangement of normal joint mechanics. However, despite considerable experimental data supporting this position, there also are theories that suggest otherwise. This illustrates a very important point in patellofemoral joint pathology, where no one factor may be the sole defining etiology. Instead, the patellofemoral joint is one of the most complex diarthrodial joints in the body and there are a number of etiologic factors that can lead to pathology. This should be considered for developing repair and rehabilitation strategies.

Influence of the infrapatellar fat pad resection in a synovectomy during total knee arthroplasty in patients with rheumatoid arthritis

Influence of the infrapatellar fat pad resection in a synovectomy during total knee arthroplasty (TKA) was evaluated in patients with rheumatoid arthritis (RA). Our findings for 120 RA patients at 28 to 38 months after surgery showed that (i) a significant decrease in the number of patients with anterior aching discomfort despite a lower-lying patella was seen in patients with infrapatellar synovectomy compared with patients without infrapatellar synovectomy, and (ii) an increase in the number of patients with anterior aching discomfort, significant limited motion, slight quadriceps weakness, and significant shortening of patellar tendon length and patella height were noted among patients with infrapatellar synovectomy, including fat pad resection, than in patients without infrapatellar synovectomy.

Electromyography of the quadriceps in patellofemoral pain with patellar subluxation

This study compared muscle activity and timing of gait phases during functional activities in 13 subjects with patellofemoral pain associated with lateral subluxation and in 11 subjects with healthy knees. Fine wire electromyography recorded activity in the vastus lateralis and vastus medialis oblique during walking and ascending and descending stairs. Subjects were filmed to divide the activities into phases and determine timing. The vastus medialis oblique and vastus lateralis had similar patterns during all activities. Subjects with patellofemoral pain had significantly increased activity in the vastus medialis oblique and vastus lateralis compared with the healthy subjects during the most demanding phases of the gait cycle, suggesting a generalized quadriceps weakness in the patients with patellofemoral pain. Timing differences were seen in walking and stair ascending with the subjects with patellofemoral pain spending significantly more time in stance compared with the healthy subjects. This may be an attempt to reduce the load on weak quadriceps. These data reflect a generalized quadriceps muscle weakness, rather than the prevailing theory of quadriceps muscle imbalance as an etiology of patellofemoral pain. Therefore, we support the practice of strengthening the entire quadriceps muscle group, rather than attempting to specifically target the vastus medialis oblique.

The effect of inturning of the foot on knee kinematics and kinetics in children with treated idiopathic clubfoot

OBJECTIVE

To assess the effect of internal foot progression angle (inturning) on knee dynamics in children with treated clubfeet.

DESIGN

Prospective study dividing a population of clubfeet according to the factor inturning.

BACKGROUND

Excessive internal or external foot progression angle increases knee flexion by a backward shift of the ground reaction force to the knee joint in children with cerebral palsy. Similarly, inturning in clubfeet was hypothesized to shift the ground reaction force backwards with reference to the knee joint, increasing the external knee flexion moment and the maximal knee flexion at stance.

METHODS

Three-dimensional gait analysis was performed on 20 children with surgically treated clubfeet (n=28) to assess alterations of knee dynamics related to inturning (>7 degrees ) and on 13 normal children.

RESULTS

Inturning occurred in 46% of the clubfeet and was associated during stance, at maximal knee flexion, to an increase in maximal knee flexion (+7 degrees ), external knee flexion moment (+60%) and related lever arm to the knee (+100%) and at minimal knee flexion, to a reduction in external knee extension moment (-62%) and related lever arm (-58%). Inturning was associated with a more frequent prolongation of internal knee extension moment and of rectus femoris activity exceeding 50% of stance.

CONCLUSION

Inturning in clubfeet is associated with knee dynamics alteration, which might contribute to the long-term development of knee osteoarthritis.

RELEVANCE

The therapeutic correction of inturning in clubfeet would be of importance if the consecutive knee dynamics alteration is shown by further studies to contribute to long-term degenerative knee pathology.

Rehabilitation After Oswestry Autologous-Chondrocyte Implantation: The OsCell Protocol

Objective:

To develop a postoperative rehabilitation protocol for patients receiving autologous-chondrocyte implantation (ACI) to repair articular-cartilage defects of the knee.

Data Sources:

careful review of both basic science and clinical literature, personal communication with colleagues dealing with similar cases, and the authors’ experience and expertise in rehabilitating numerous patients with knee pathologies, injuries, and trauma.

Data Synthesis:

Postoperative rehabilitation of the ACI patient plays a critical role in the outcome of the procedure. The goals are to improve function and reduce discomfort by focusing on 3 key elements: weight bearing, range of motion, and strengthening.

Conclusions:

The authors present 2 flexible postoperative protocols to rehabilitate patients after an ACI procedure to the knee.

Comparison of the LISS and a retrograde-inserted supracondylar intramedullary nail for fixation of a periprosthetic distal femur fracture proximal to a total knee arthroplasty

Simulated supracondylar fractures were created proximal to posterior cruciate ligament-retaining total knee arthroplasty components in paired human cadaver femora and stabilized with either a retrograde-inserted locked supracondylar nail or the Less Invasive Stabilization System (LISS; Synthes USA, Paoli, PA). Loads were applied to create bending and torsional moments on the simulated fracture stabilized with either no gap or a 10-mm gap. The LISS exhibited less torsional stability with anterior (P<.001) and posterior loads (P<.01). When varus loads were applied to 10-mm-gap specimens, the specimens stabilized with a retrograde nail had an 83% reduction in fracture displacement (P<.001) and 80% less medial translation of the distal fragment (P<.001). The samples stabilized with the LISS had a 93% reduction in fracture gap displacement when a valgus load was applied with a 10-mm gap (P<.001). Overall, these results suggest that the retrograde-inserted nail may provide greater stability for the management of periprosthetic supracondylar femur fractures in patients with a posterior cruciate ligament-retaining femoral total knee arthroplasty component.

Patellofemoral stress during walking in persons with and without patellofemoral pain

OBJECTIVE

To determine whether individuals with patellofemoral pain (PFP) demonstrate elevated patellofemoral joint (PFJ) stress compared with pain-free controls during free and fast walking.

DESIGN

A cross-sectional study utilizing an experimental and a control group.

BACKGROUND

Although the cause of PFJ pathology is believed to be related to elevated joint stress (force per unit area), this hypothesis has not been adequately tested and causative mechanisms have not been clearly defined.

METHODS

Ten subjects with a diagnosis of PFP and 10 subjects without pain participated. All subjects completed two phases of data collection: 1) magnetic resonance imaging (MRI) assessment to determine PFJ contact area and 2) comprehensive gait analysis during self-selected free and fast walking velocities. Data obtained from both phases were required as input variables into a biomechanical model to quantify PFJ stress.

RESULTS

On the average, PFJ stress was significantly greater in subjects with PFP compared with control subjects during level walking. The observed increase in PFJ stress in the PFP group was attributed to a significant reduction in PFJ contact area, as the PFJ reaction forces were similar between groups.

CONCLUSION

Our results are consistent with the hypothesis that increased patellofemoral joint stress may be a predisposing factor with respect to development of PFP. Clinically, these findings indicate that treatments designed to increase the area of contact between the patella and the femur may be beneficial in reducing the PFJ stress during functional activities.

RELEVANCE

Patellofemoral pain affects about 25% of the population, yet its etiology is unknown. Knowledge of the biomechanical factors contributing to patellofemoral joint pain may improve treatment techniques and guide development of prevention strategies.

Patellofemoral joint kinetics while squatting with and without an external load

STUDY DESIGN

Single-group repeated measures design.

OBJECTIVE

To quantify patellofemoral joint reaction forces and stress while squatting with and without an external load.

BACKGROUND

Although squatting exercises in the rehabilitation setting are often executed to a relatively shallow depth in order to avoid the higher joint forces associated with increased knee flexion, objective criteria for ranges of motion have not been established.

METHODS AND MEASURES

Fifteen healthy adults performed single-repetition squats to 90 degrees of knee flexion without an external load and with an external load (35% of the subject's body weight [BW]). Anthropometric data, three-dimensional kinematics, and ground reaction forces were used to calculate knee extensor moments (inverse dynamics approach), while a biomechanical model of the patellofemoral joint was used to quantify the patellofemoral joint reaction forces and patellofemoral joint stress. Data were analyzed during the eccentric (0-90 degrees) and concentric (90-0 degrees phases of the squat maneuver.

RESULTS

In both conditions, knee extensor moments, patellofemoral joint reaction forces, and patellofemoral joint stress increased significantly with greater knee flexion angles (P < 0.05). Peak patellofemoral joint force and stress was observed at 90 degrees of knee flexion. Patellofemoral joint stress at 45 degrees, 60 degrees, 75 degrees, and 90 degrees of knee flexion during the eccentric phase, and at 75 degrees and 90 degrees during the concentric phase, was significantly greater in the loaded trials versus the unloaded trials.

CONCLUSION

The data indicate that during squatting, patellofemoral joint stress increases as the knee flexion angle increases, and that the addition of external resistance further increases patellofemoral joint stress. These findings suggest that in order to limit patellofemoral joint stress during squatting activities, clinicians should consider limiting terminal joint flexion angles and resistance loads.

The effects of patellar taping on knee kinetics, kinematics, and vastus lateralis muscle activity during stair ambulation in individuals with patellofemoral pain

STUDY DESIGN

Pre- and postintervention repeated measures design.

OBJECTIVE

To determine the effects of patellar taping on knee kinetics, kinematics, and vastus lateralis muscle activity during stair ambulation in individuals with patellofemoral pain (PFP).

BACKGROUND

Patellar taping is a common treatment technique for individuals with PFP. Specific data on whether patellar taping improves gait variables, however, are limited.

METHODS AND MEASURES

Ten subjects with a diagnosis of PFP were studied (five men, five women). The subjects' mean age, height, and mass were 36.5 +/- 11.1 years, 173.1 +/- 10.3 cm, and 70.9 +/- 13.3 kg, respectively. Lower extremity kinematics, ground reaction forces, and vastus lateralis EMG were obtained simultaneously while subjects ascended and descended stairs, under taped and untaped conditions. Knee moments were calculated using inverse dynamics equations. Four 2 x 2 (tape condition x stair condition) ANOVAs for repeated measures were generated for cadence and average stance phase knee extensor moment, knee flexion angle, and EMG.

RESULTS

On the average, a 92.6% reduction in pain was observed following the application of tape. Increases in cadence, knee flexion angles, and knee extensor moments were observed under the taped condition for both stair ascent and descent; however, no difference in average vastus lateralis EMG was found.

CONCLUSIONS

Although patellar taping resulted in decreased pain and increased knee extensor moments, knee flexion angles, and cadence during stair ambulation, the vastus lateralis EMG activity level did not change with taping. Based on data from the vastus lateralis, care must be taken if improved gait parameters indicate change in muscle recruitment.

Lower extremity kinetics during stair ambulation in patients with and without patellofemoral pain

OBJECTIVE

To compare lower extremity kinetics during stair ascent and descent in subjects with and without patellofemoral pain.

DESIGN

A cross-sectional study utilizing a control group.

BACKGROUND

The patellofemoral joint reaction force (the resultant force between the quadriceps muscle force and patellar ligament force) increases with quadriceps force and knee flexion angle. Consequently, patients with patellofemoral pain may employ compensatory strategies to minimize pain and reduce patellofemoral joint reaction forces during activity.

METHODS

10 individuals with a diagnosis of patellofemoral pain and 10 individuals without pain participated. Subject groups were matched on sex, age, height, and body mass. Anthropometric data, three dimensional kinematics, and ground reaction forces were used to calculate lower extremity sagittal plane moments (inverse dynamics) while subjects ascended and descended stairs at a self-selected pace. Differences in kinetic variables between groups were assessed using 2x2 (group x stair condition) analysis of variance.

RESULTS

Subjects with patellofemoral pain had decreased peak knee extensor moments during stair ascent and descent. There were no group differences in peak hip, ankle, or support moments, however, subjects with patellofemoral pain had decreased cadence (descent) compared to controls.

CONCLUSION

Subjects with patellofemoral pain had reduced peak knee extensor moments, suggesting that quadriceps avoidance was employed to reduce patellofemoral joint reaction forces. The lack of group differences in peak moments at the hip and ankle suggests that secondary compensation did not occur exclusively at the hip or ankle in this group of subjects with patellofemoral pain. RELEVANCE STATEMENT: Because stair ambulation is often used to evaluate the reproducibility of symptoms and to identify abnormal movement patterns indicative of patellofemoral pain, knowledge of lower extremity mechanics during stair negotiation is necessary to better characterize compensatory behavior in this population.

The influence of femoral rollback on patellofemoral contact loads in total knee arthroplasty

Increasing femoral rollback in flexion is thought to reduce patellofemoral contact load in total knee arthroplasty (TKA). The objectives of this study were to quantify the dependence of patellar load on rollback and to assess the effectiveness of posterior cruciate ligament (PCL)-retaining, PCL-sacrificing, and PCL-substituting TKA types in generating rollback. Nine cadaver knees were tested in simulated squatting. Six TKAs that were expected to produce varying amounts of femoral rollback were evaluated: PCL-retaining TKA, PCL-sacrificing TKA, a commercially available PCL-substituting TKA, and 3 modified PCL-substituting TKAs in which the anteroposterior position of the tibial post was varied. Kinematics, quadriceps loads, and patellofemoral contact loads were recorded. Significant differences in rollback were observed in the 30 degrees to 90 degrees flexion range. PCL-sacrificing TKAs generated the least rollback. PCL-retaining TKAs produced greater rollback but had the most variability. PCL-substituting TKAs produced the greatest and most reproducible rollback. Moving the tibial post posteriorly further increased rollback. Increased rollback correlated with reduced patellar load (-2.2%/mm). Reductions in patellar load of 17.6% were observed. Quadriceps loads were reduced by increasing rollback but to a smaller degree (-0.9%/mm). Rollback primarily affects patellar load rather than quadriceps load or efficiency.

Effects of technique variations on knee biomechanics during the squat and leg press

PURPOSE

The specific aim of this project was to quantify knee forces and muscle activity while performing squat and leg press exercises with technique variations.

METHODS

Ten experienced male lifters performed the squat, a high foot placement leg press (LPH), and a low foot placement leg press (LPL) employing a wide stance (WS), narrow stance (NS), and two foot angle positions (feet straight and feet turned out 30 degrees ).

RESULTS

No differences were found in muscle activity or knee forces between foot angle variations. The squat generated greater quadriceps and hamstrings activity than the LPH and LPL, the WS-LPH generated greater hamstrings activity than the NS-LPH, whereas the NS squat produced greater gastrocnemius activity than the WS squat. No ACL forces were produced for any exercise variation. Tibiofemoral (TF) compressive forces, PCL tensile forces, and patellofemoral (PF) compressive forces were generally greater in the squat than the LPH and LPL, and there were no differences in knee forces between the LPH and LPL. For all exercises, the WS generated greater PCL tensile forces than the NS, the NS produced greater TF and PF compressive forces than the WS during the LPH and LPL, whereas the WS generated greater TF and PF compressive forces than the NS during the squat. For all exercises, muscle activity and knee forces were generally greater in the knee extending phase than the knee flexing phase.

CONCLUSIONS

The greater muscle activity and knee forces in the squat compared with the LPL and LPH implies the squat may be more effective in muscle development but should be used cautiously in those with PCL and PF disorders, especially at greater knee flexion angles. Because all forces increased with knee flexion, training within the functional 0-50 degrees range may be efficacious for those whose goal is to minimize knee forces. The lack of ACL forces implies that all exercises may be effective during ACL rehabilitation.

Kinematics of the patellofemoral joint in total knee arthroplasty

Sagittal plane patellofemoral kinematics was determined for 81 subjects while performing a weight-bearing deep knee bend under fluoroscopic surveillance. Fourteen normal knees, 12 anterior cruciate ligament (ACL)-deficient knees, and 55 total knee arthroplasties (TKAs) were assessed. Of TKAs, 39 had resurfacing with a dome-shaped patella, 8 had resurfacing with an anatomic mobile-bearing patella, and 8 were unresurfaced. TKA patellae experienced more superior patellofemoral contact and higher patellar tilt angles compared with the normal knees and ACL-deficient knees (P <.05). Patellofemoral separation at 5 degrees (+/-3 degrees ) extension was seen in 86% cruciate-retaining and 44% cruciate-stabilized TKAs and 8% ACL-deficient knees but not in the normal knees or mobile-bearing TKAs (P <.05). The patellar kinematic patterns for subjects having a TKA were more variable than subjects having either a normal knee or an ACL-deficient knee. Kinematic abnormalities of the prosthetic patellofemoral joint may reduce the effective extensor moment after TKA.

Patellofemoral joint kinetics during squatting in collegiate women athletes

OBJECTIVE

To characterize the biomechanics of the patellofemoral joint during squatting in collegiate women athletes.

DESIGN

Repeated measures experimental design.

BACKGROUND

Although squatting exercises are required components of most intercollegiate resistance-training programs and are commonly performed during rehabilitation, the effects of various squatting depths on patellofemoral joint stress have not been quantified.

METHODS

Anthropometric data, three-dimensional knee kinematics, and ground reaction forces were used to calculate the knee extensor moment (inverse dynamics approach) in five intercollegiate female athletes during squatting exercise at three different depths (approximately 70 degrees, 90 degrees and 110 degrees of knee flexion). A biomechanical model of the patellofemoral joint was used to quantify the patellofemoral joint reaction force and patellofemoral joint stress during each trial.

RESULTS

Peak knee extensor moment, patellofemoral joint reaction force and patellofemoral joint stress did not vary significantly between the three squatting trials.

CONCLUSIONS

Squatting from 70 degrees to 110 degrees of knee flexion had little effect on patellofemoral joint kinetics. The relative constancy of the patellofemoral joint reaction force and joint stress appeared to be related to a consistent knee extensor moment produced across the three squatting depths.

RELEVANCE

The results of this study do not support the premise that squatting to 110 degrees places greater stress on the patellofemoral joint than squatting to 70 degrees. These findings may have implications with respect to the safe design of athletic training regimens and rehabilitation programs.

Women's shoes and knee osteoarthritis

We assessed whether wearing wide-heeled shoes has a similar effect on knee torque to narrow-heeled shoes by measuring the joint torques of 20 healthy women during walking. Wearing wide-heeled shoes had a 30% greater effect on peak external knee flexor torque than walking barefoot. Walking with wide-heeled and narrow-heeled shoes increased peak knee varus torque by 26% and 22%, respectively. Our findings imply that wide-heeled shoes cause abnormal forces across the patellofemoral and medial compartments of the knee, which are the typical anatomical sites for degenerative joint changes.

A Mathematical Formulation for 3D Quasi-Static Multibody Models of Diarthrodial Joints

This study describes a general set of equations for quasi-static analysis of three-dimensional multibody systems, with a particular emphasis on modeling of diarthrodial joints. The model includes articular contact, muscle forces, tendons and tendon pulleys, ligaments, and the wrapping of soft tissue structures around bone and cartilage surfaces. The general set of equations governing this problem are derived using a consistent notation for all types of links, which can be converted conveniently into efficient computer codes. The computational efficiency of the model is enhanced by the use of analytical Jacobians, particularly in the analysis of articular surface contact and wrapping of soft tissue structures around bone and cartilage surfaces. The usefulness of the multibody model is demonstrated by modeling the patellofemoral joint of six cadaver knees, using cadaver-specific data for the articular surface and bone geometries, as well as tendon and ligament insertions and muscle lines of actions. Good accuracy was observed when comparing the model patellar kinematic predictions to experimental data (mean +/- stand. dev. error in translation: 0.63 +/- 1.19 mm, 0.10 +/- 0.71 mm, -0.29 +/- 0.84 mm along medial, proximal, and anterior directions, respectively; in rotation: -1.41 +/- 1.71 degrees, 0.27 +/- 2.38 degrees, -1.13 +/- 1.83 degrees in flexion, tilt and rotation, respectively). The accuracy which can be achieved with this type of model, and the computational efficiency of the algorithm employed in this study may serve in many applications such as computer-aided surgical planning, and real-time computer-assisted surgery in the operating room.