Gait Biomechanics During Early Stance Phase Predict Pain Flares in Persons With Patellofemoral Joint Osteoarthritis

OBJECTIVE: To examine gait mechanics associated with the occurrence of a movement-evoked pain flare in individuals with patellofemoral joint osteoarthritis (PFJOA). DESIGN: Cross-sectional observational study. METHODS: Twenty-two participants with PFJOA and 10 healthy control participants completed five overground gait trials at a fixed speed of 1.35 m/s ± 5%. Lower limb kinematics and kinetics were recorded using motion capture and in-ground force plates. PFJOA participants completed a 20-minute decline treadmill walk, rating pain every minute via the numeric pain rating scale (NPRS). Participants were grouped based on change in NPRS [≥2-point increase = pain flare (PF); <2-point = no flare (NF)]. ANOVA and posthoc analyses compared gait mechanics between groups (PF, NF, and C [control]). RESULTS: During the first half of stance, people with pain flares (n = 12) had higher peak knee flexion angle (17.7 ± 2.4) compared to controls (13.6 ± 3.4; p = .003) and higher knee flexion moment (KFM) impulse (0.62 ± 0.11) compared to people with no pain flare (n = 10) (0.45 ± 0.19; p = 0.001) and to controls (0.39 ± 0.12; p = .0001). The no pain flare group had lower knee adduction moment (KAM) impulse (0.45 ± 0.16) compared to controls (0.61 ± 0.12; p = .04). In the second half of stance, the no pain flare group had higher knee external rotation angles (8.7 ± 5.2) compared to the pain flare group (4.9 ± 3.0; p = 0.02) and to controls (4.5 ± 2.9; p = .009). CONCLUSIONS: People with PFJOA and who were prone to movement-evoked pain flares had increased sagittal plane loading during gait, while those without flares had reduced frontal plane loading and greater knee external rotation angles. Further investigation into a causal relationship between these gait alterations and movement-evoked pain would provide valuable insight for treatment of patients with PFJOA.