Patellofemoral Joint Kinetics While Squatting with and without an External Load

Abstract

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°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°) and concentric (90-0°) 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 Ͻ 0.05). Peak patellofemoral joint force and stress was observed at 90°of knee flexion. Patellofemoral joint stress at 45°, 60°, 75°, and 90°of knee flexion during the eccentric phase, and at 75°and 90°d uring 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.

Femur Rotation and Patellofemoral Joint Kinematics: A Weight-Bearing Magnetic Resonance Imaging Analysis

“…Although the group differences in medial femoral rotation were less pronounced with the knee flexed to 30° and 45°, only a slight decrease in contact area would be needed to increase patellofemoral stress, as the joint reaction forces are known to be greater with increasing knee flexion during weight bearing. 33 The cause of the excessive medial rotation of the femur in the PFP group was not assessed in the current study, so it is unclear if the observed kinematics were the cause of PFP, the result of PFP, or merely an association. However, proposed mechanisms include skeletal abnormalities (femoral anteversion, trochlear dysplasia, and patella dysplasia), 1,2,25 and diminished hip muscle performance.…”

Analysis of Hip Strength in Females Seeking Physical Therapy Treatment for Unilateral Patellofemoral Pain Syndrome

“…The clinical diagnosis of PFPS typically encompasses retropatellar and/or peripatellar knee pain that is aggravated by prolonged sitting or activities that load the patellofemoral joint, such as ascending or descending stairs, squatting, running, jumping, or kneeling. 4,27 The most commonly accepted hypothesis of the cause of PFPS is that abnormal patellar tracking increases patellofemoral joint stress and causes t Study deSign: Cross-sectional.…”

The Influence of Tibial and Femoral Rotation on Patellofemoral Contact Area and Pressure

“…22,24 These results have been used to explain the clinical observation that chondral degeneration seen in patellofemoral pain is most likely to occur in areas that correspond to those contact areas seen between 40°and 80°of knee flexion. Wallace et al 52 demonstrated that statistically significant increases in patellofemoral stress were seen with greater knee flexion angles during a loaded and unloaded squat. Patellofemoral stress increased from 30°to 90°, peaking at 90°for both eccentric and concentric muscle contractions.…”