Tibiofemoral Forces Research Articles

Rehabilitation Programs for the PCL-Injured and Reconstructed Knee

Treatment of posterior cruciate ligament (PCL) injuries has changed considerably in recent years. This article discusses current rehabilitation for PCL disruptions in athletes. The treatment of PCL injuries varies somewhat based on the chronicity (acute vs. chronic) of injury and associated pathologies. The authors provide their treatment algorithm for the acute and chronic PCL-injured-knee patient. Nonoperative rehabilitation is discussed with a focus on immediate motion, quadriceps muscle strengthening, and functional rehabilitation. A discussion of the biomechanics of exercise is provided, with a focus on tibiofemoral shear forces and PCL strains. Surgical treatment is also discussed, with the current surgical approach being either the two-tunnel or the one-tunnel patellar tendon autograft procedure. The rehabilitation program after surgery is based on the healing constraints, surgical technique, biomechanics of the PCL during functional activities, and exercise. With the new changes in surgical technique and in the rehabilitation process, the authors believe that the outcome after PCL reconstruction will be enhanced.

Knee joint forces during downhill walking with hiking poles

The aim of this study was to determine external and internal loads on the knee joint during downhill walking with and without hiking poles. Kinematic, kinetic and electromyographic data were collected from eight males during downhill walking on a ramp declined at 25 o . Planar knee joint moments and forces were calculated using a quasi-static knee model. The results were analysed for an entire pole-cycle as well as differentiated between single and double support phases and between each step of a pole-cycle. Significant differences between downhill walking with and without hiking poles were observed for peak and average magnitudes of ground reaction force, knee joint moment, and tibiofemoral compressive and shear forces (12-25%). Similar reductions were found in patellofemoral compressive force, the quadriceps tendon force and the activity of the vastus lateralis; however, because of a high variability, these differences were not significant. The reductions seen during downhill walking with hiking poles compared with unsupported downhill walking were caused primarily by the forces applied to the hiking poles and by a change in posture to a more forward leaning position of the upper body, with the effect of reducing the knee moment arm.

BIOMECHANICS OF THE KNEE DURING CLOSED KINETIC CHAIN AND OPEN KINETIC CHAIN EXERCISES

269 Although closed (CKCE) and open (OKCE) kinetic chain exercises are used in athletic training and clinical environments, there are currently no data comparing knee joint biomechanics while performing these exercises dynamically. The purpose of this study was to quantify knee forces and muscle activity during CKCE (squat and leg press) and OKCE (knee extension). Ten male subjects performed three repetitions of each exercise at their 12-repetition maximum. Kinematic, kinetic and electromyographic data were calculated using video cameras (60 Hz), force transducers (960 Hz) and EMG (960 Hz). Mathematical muscle modelling and optimization techniques were employed to estimate muscle and ligamentous forces. Quadriceps activity was significantly greater in OKCE near full knee extension and greater in CKCE near full flexion. Hamstring activity remained low throughout the leg press and OKCE. During the knee-extending phase the squat generated significantly greater hamstring activity than the leg press and OKCE. Tibiofemoral compressive force was greatest in OKCE near full knee extension and greatest in CKCE near full knee flexion. For all exercises, approximately 3000 N of maximum tibiofemoral force was produced. Maximum tibiofemoral force was produced between 53-93° knee angle during CKCE and between 39-57 ° during OKCE. For all exercises, PCL tensile forces generally increased with knee flexion and decreased with knee extension. During CKCE, the PCL was always in tension. During OKCE, the PCL was in tension at greater than 25 ° knee angle, while the ACL was in tension near full knee extension (15-25 °). Peak PCL forces were near 2000 N for CKCE and near 1000 N for OKCE. Patellofemoral forces generally increased with knee flexion and decreased with knee extension. OKCE produced significantly greater patellofemoral forces than CKCE at knee angles less than 57 °, while CKCE generated significantly larger patellofemoral forces than OKCE at knee angles greater than 85 °. Maximum patellofemoral force exceeded 4000 N for all three exercises. An understanding of these results can help in balancing muscle strengthening with ligament and bone loading.

THE EFFECTS OF TECHNIQUE VARIATIONS ON KNEE BIOMECHANICS DURING THE SQUAT AND LEG PRESS 887

The current study quantified tibiofemoral compressive force, patellofemoral compressive force, and cruciate ligamentous (ACL/PCL) tensile force during a dynamic barbell parallel squat (SQ) and Body Master (MD-117) leg press (LP) using varying stances (narrow and wide), foot angles (straight and turned out 30°), and foot placements (high and low). Ten experienced weight lifters served as subjects, using their 12 repetition maximum weight. A four camera motion analysis system collected 60 Hz video data from reflective markers positioned over bony landmarks, while two AMTI force platforms were used to collect 960 Hz kinetic data. Resultant knee forces were calculated as functions of knee angle utilizing 3-D rigid link models and inverse dynamics. Mathematical muscle models were developed and optimizations procedures utilized in order to estimate tibiofemoral, cruciate ligamentous, and patellofemoral forces. Foot angle and foot placement variations did not significantly effect knee forces. During the SQ and LP peak tibiofemoral, PCL, and patellofemoral forces were approximately 3300N, 2000N, and 4800N, respectively, and occurred near maximum knee flexion. The wide stance (WS) and narrow stance (NS) SQ generated significantly greater tibiofemoral force than both LP exercises throughout most of the knee flexion and knee extension ranges, with the WS SQ generating significantly greater force than the NS SQ. The SQ generated significantly greater PCL tension than both LP exercises, with few significant differences between stance variations. Patellofemoral forces were significantly greater in the WS SQ compared to the LP during knee flexion, while the NS LP produced significantly greater forces than the SQ and WS LP during knee extension. Peak patellofemoral forces were greatest during the NS LP. The greater tibiofemoral forces generated during the SQ may help protect the knee against excessive shear forces. No ACL tension was generated in the SQ and LP, while the SQ generally generated the greatest PCL tension. The greatest patellofemoral forces generated during the NS LP may predispose the patellofemoral joint to increased risk of chondromalacia or osteoarthritis compared to the SQ or WS LP exercises.

Instrumented implant for measuring tibiofemoral forces

Experimental measurement of loads occurring in the human knee joint will allow validation of analytical models and provide data for the design of total knee implants. A customized transducer was developed to measure the dynamic tibiofemoral force and center of pressure after total knee arthroplasty. The transducer consists of a standard tibial component to which four uniaxial load cells and an additional tibial tray have been added. The transducer was calibrated using a loading device traceable to the National Institute of Standards and Technology (NIST). The transducer was accurate to within 1% in magnitude, 0.07 mm in medial/lateral location and 0.24 m in anterior/posterior location.

Muscular and tibiofemoral joint forces during isokinetic concentric knee extension

The purpose of this study was the examination of muscular and tibiofemoral forces during concentric isokinetic knee extension at angular velocities ranging from 30 to 210 deg s −1, using a two-dimensional biomechanical model. Five males without knee joint injury history participated in the study. The maximum moment ranged from 226.2 Nm at 30 deg s −1 to 166.4 Nm at 210 deg s −1. The maximum muscular force ranged from 7.5 times body weight at 30 deg s −1 to 5.7 at 210 deg s −1. The compressive tibiofemoral force ranged from 7.5 times body weight at 30 deg s −1 to 5.7 at 210 deg s −1 and the shear tibiofemoral force ranged from 0.9 to 0.8 times body weight respectively. These results indicate that the forces developed during maximal isokinetic knee extension are significantly reduced relative to other powerful dynamic activities but are higher than joint forces during simple walking and cycling activities. Appropriate precautions and adjustment of the isokinetic protocol are required in the final phases of joint injury rehabilitation.

Tibiofemoral joint forces during ergometer cycling

Six healthy subjects pedaled on a weight-braked bicycle ergometer at different workloads, pedaling rates, saddle heights, and pedal foot positions. The subjects were filmed with a cine-film camera and pedal reaction forces were recorded from a force transducer mounted on the left pedal. Net knee moments were calculated using a dynamic model, and the tibiofemoral shear and compressive force magnitudes were calculated using a biomechanical model of the knee. During cycling at 120 W, 60 rpm, midsaddle height, and anterior pedal foot position, the mean peak tibiofemoral compressive force was 812 N [1.2 times body weight (BW)]. The maximum anteriorly directed tibiofemoral shear force was found to be low (37 N). The compressive and shear forces were significantly increased by an increased ergometer workload. The pedaling rate had no influence on the tibiofemoral force magnitudes. The stress on the ACL was low and could be further decreased by use of the anterior foot position instead of the posterior.

Joint forces in extension of the knee. Analysis of a mechanical model.

A two-dimensional model of the tibio-femoral joint was constructed by using the results of cadaver knee dissections together with radiographic landmarks on healthy knees loaded at various angles of flexion. The tibio-femoral compressive force during isometric knee extension had the same magnitude as the patellar tendon force. The tibio-femoral shear force changed direction from posterior at full flexion to anterior when the knee was extended, indicating that high forces may arise in the anterior cruciate was extended, indicating that high forces may arise in the anterior cruciate ligament in the straight knee. Women developed some 20 per cent higher knee joint forces than men for the same extending muscular moment higher knee joint forces than men for the same extending muscular moment, since women's patellar tendon moment arms were found to be shorter. The model presented may be used for quantifying tibio-femoral forces during knee extending activities.

Axisymmetric finite element analysis of the lateral tibial plateau

An axisymmetric finite element code was used to predict stresses and displacements in the proximal tibia of the human knee. Joint geometries were determined from a midfrontal section of a normal lateral tibial plateau. Constitutive relations, tibiofemoral forces and joint contact areas were estimated from the literature. Fourier expansions were used to provide localized loading over the assumed contact region. The results emphasize that subchondral trabecular bone serves to transmit the large loads applied to the cartilage surface by gradually concentrating these loads into the compact bone of the tibial diaphysis. The model predicts a nearly hydrostatic stress state in articular cartilage within the contact region and high tensile principal strains at the edge of the contact region. For trabecular bone, the model predicts maximum compressive stresses beneath the center of the contact region and maximum shear stresses beneath the edge of the contact region. The predicted principal stress directions in the continuum representation for trabecular bone also bear a strong resemblance to the trabecular architecture of the lateral tibial plateau.