A musculoskeletal model with modified patellofemoral kinematics for improved patellar tendon force estimations across motions with a large range of knee flexion.

Abstract

The estimation of patellar tendon force (PTF) is critical for understanding musculoskeletal loading during physical activity. Accurate PTF estimations, particularly during exercises involving deep knee flexion such as lunges and squats, depend heavily on the patellar tendon moment arm (PTMA). This study aimed to evaluate the implementation of a revised PTMA and accompanying patellofemoral kinematics in a contemporary musculoskeletal model to improve PTF estimations across knee flexion angles ranging from 10 to 100 degrees. Biomechanical data were collected from 14 participants (7 with patellar tendinopathy and 7 healthy individuals) performing various exercises. Model revisions incorporated modified patellofemoral kinematics to better align the PTMA of the model with prevailing PTMA reference data. Peak PTF values were compared between the original and updated model, and estimated muscle activations were compared with measured muscle activations for both models. Results showed that the updated model yielded improved agreement between estimated and measured muscle activations. In conclusion, the updated model demonstrated better construct validity, particularly for exercises involving knee flexion beyond 50 degrees, and is recommended for future applications in musculoskeletal research.