Foot and ankle characteristics and dynamic knee valgus in individuals with patellofemoral osteoarthritis

STUDY DESIGN: Controlled laboratory study; cross-sectional design. BACKGROUND: Foot and ankle characteristics and dynamic knee valgus differ in people with and without patellofemoral (PF) pain. However, it is unknown if these characteristics are evident in people with PF osteoarthritis (OA), compared to pain-free older adults. OBJECTIVES: To compare foot and ankle mobility, foot posture and dynamic knee valgus, measured as the frontal plane projection angle (FPPA) during single-leg squatting, between individuals with and without PFOA. METHODS: Fifty-one participants with PFOA (66% women, mean ± SD age 57 ± 10 years, body mass index (BMI) 27 ± 6 kg/m(2)), and 23 controls (56% women, age 56 ± 9 years, BMI 24 ± 4 kg/m(2)) had ankle dorsiflexion measured using the knee-to-wall test, foot mobility calculated as the difference in midfoot height or width between non-weightbearing and weightbearing, and static foot posture characterized utilizing the Foot Posture Index. Peak FPPA was determined from video recordings while participants performed 5 single-leg squats. Linear regressions examined between-groups relationships for foot and ankle characteristics and the FPPA. RESULTS: The PFOA group had less ankle dorsiflexion (odds ratio 6.7, 95% confidence interval 2.46–18.2), greater midfoot height mobility (5.2, 1.78–15.14) and width mobility (4.3, 1.33–14.39), and greater foot mobility magnitude (8.4, 2.32–30.69) than controls. There was no difference in FPPA (knee valgus angle) between groups (15, 0.63–377.99). CONCLUSION: Foot and ankle characteristics were different in individuals with PFOA compared to control participants, however there was no difference in dynamic knee valgus during single leg squat. Clinical interventions to address greater foot mobility may be relevant for PFOA.