Patients with patellofemoral pain have lower soft tissue flexibility of the kinetic chain compared to healthy controls: A case-control study

Introduction: Patellofemoral pain (PFP) is a common musculoskeletal condition. Lower limb range of motion (LLROM) evaluates soft tissue flexibility over multiple joints as part of the kinetic chain. The aims were to study: 1) the reliability of a new LLROM test; 2) differences in LLROM between PFP patients and controls; and 3) the relationship between LLROM and pain-free knee function. Methods: Patients with PFP and matched controls were recruited from a university campus and private physiotherapy clinics, while observers were blinded for health status. Testing LLROM for maximal knee flexion and hip adduction and the sum of these (total ROM) were performed. Measures of reliability (ICC2,1) were established. Univariate linear regression between LLROM and health status and multivariate analysis between LLROM and knee function were performed. Results: Patients (n = 32 (7 male/25 female, age = 22, BMI = 22.7)) and controls (n = 32 (7 male/25 female, age = 20, BMI = 22.3)) were included. The ICC's for intra- and interobserver reliability ranged from 0.83 (95%CI 0.30–0.93) to 0.89 (0.72–0.95). Symptomatic legs had 7°(3–11, p = 0.014) lower knee flexion, 6°(4–8, p ≤ 0.001) lower hip adduction and 13°(8–17, p ≤ 0.001) lower total ROM than non-symptomatic legs. Multivariate analysis revealed an association between total ROM and pain-free knee function (R2 = 0.438, F = 6.544, p ≤ 0.001). Conclusions: The new LLROM test was found to be reliable. Patients with PFP had lower LLROM, which was associated with impaired pain-free knee function. Whether improving soft tissue flexibility results in enhanced pain-free knee function should be the subject of future research.