Patellofemoral instability (PFI) is a common musculoskeletal disorder involving lateral patellar subluxation or dislocation. This condition occurs most commonly during adolescence, with over 50% of this demographic experiencing recurrent dislocations, which can lead to longstanding issues 1. Morphologic features in the knee have been associated with increased risk of injury or pathology 2, however, the ability to measure PF joint function in vivo is challenging. Therefore, this research seeks to use patient-specific knee models to investigate variability in knee mechanics between adolescents with and without a history of PFI during dynamic tasks. Six adolescents (three controls and three with a history of PFI) were enrolled in this study. An MRI of the dominant or symptomatic knee was obtained, and the patients subsequently underwent gait and lunge trials at the human movement biomechanics laboratory. The MRIs were segmented to produce a patient-specific model of the bone and cartilage of the femur, tibia and patella. These models were then integrated into a validated musculoskeletal model. The participant's gait and lunge trials were then simulated through inverse kinematics. The cartilage contact pressure and knee kinematics were calculated using the Concurrent Optimization of Muscle Activations and Kinematics (COMAK) routine 3. The resulting knee kinematics and contact mechanics in both the tibiofemoral (TF) and PF joints were compared throughout the tasks to assess the variability of functional knee mechanics between individuals with and without PFI. The findings from this research emphasized changes in joint kinematics and cartilage contact pressure during dynamic tasks between the two groups. At the PF joint, the PFI participants displayed higher instances of lateral patellar translation compared to the control participants during stance phase (U = 491, P-value = < 0 .001), lunge descent (U = 1273, P-value = < 0 .001), and lunge ascent (U = 0, P-value = < 0 .001; Fig. 1). Furthermore, they displayed lower cartilage contact pressure compared to the control participants during stance phase (U = 6474, P-value = < 0 .001), and lunge ascent (U = 7356, P-value = < 0 .001), as well as a much lower contact area that is more medially located for all three movements (Fig. 2). These findings agree with previous studies regarding biomechanical variations in PFI populations 4. In summary, there were noticeable differences in PF biomechanics in terms of both kinematic and kinetic measures between the two models. In these preliminary results from an ongoing study, there were noticeable differences in PF biomechanics in terms of both kinematic and kinetic measures between the two groups. Due to the difficulties of analysing PF biomechanics in vivo, this study demonstrates how these models can be used to improve our understanding of PF (dys)function to help guide injury prevention and surgical intervention strategies. For any figures or tables, please contact the authors directly.
Macie et al. (Wed,) studied this question.