Patellofemoral Pain After Knee Trauma: Exploring Clinical, Biomechanical, and Muscle Strength Variables

It remains unclear whether people with traumatic-onset patellofemoral pain (PFP_T) present with the same physical and non-physical changes as people with gradual-onset patellofemoral pain (PFP_A). In this cross-sectional study, we aimed to compare clinical, biomechanical and muscle strength outcomes between people with PFP_T, people with PFP_A, pain-free controls with a history of knee trauma (CTRL_T), and pain-free controls without a history of knee trauma (CTRL_A). Clinical variables included pain-related characteristics, time since knee trauma, kinesiophobia, and functional capacity (e.g., self-reported, objective). We captured kinematics and kinetics during a single-leg landing task, and maximal isometric torque of the knee extensors and flexors, and the hip abductors using an isokinetic dynamometer. We performed between-group comparisons using generalized linear models and independent t-tests. The PFP_T group reported higher pain, greater kinesiophobia, and lower self-reported function compared with the PFP_A group. The PFP_T group also demonstrated greater peak trunk flexion, greater peak hip flexion, and a lower knee contribution to the total support moment (TSM) compared with the PFP_A group. Both the PFP_T and PFP_A groups demonstrated reduced isometric peak torque of the knee extensors compared with the CTRL_T group. The CTRL_T group demonstrated higher peak hip flexion, lower knee contribution to TSM, and greater patellofemoral joint stress compared with CTRL_A. People with PFP_T demonstrated a worse clinical profile and a more hip-dominant landing strategy compared with those with PFP_A. Most impairments (e.g., landing biomechanics and muscle strength) were evident only in comparison with CTRL_T, who also differed clinically and mechanically from CTRL_A.