Can hip extensor strength influence the knee osteoarthritis severity? A cross-sectional analysis.

Abstract

Knee osteoarthritis (KOA) is a prevalent musculoskeletal disorder characterized by pain, functional impairment, and structural degeneration. While quadriceps and hip abductor weakness are well-established in KOA, the role of hip extensor strength remains underexplored despite its biomechanical importance in lower limb alignment and joint loading. This cross-sectional study aimed to examine whether hip extensor strength differs between asymptomatic individuals and symptomatic KOA patients, and its relationship with pain, function, and radiographic severity. Adults aged 45-70 years ( N = 112; 56 asymptomatic, 56 symptomatic for KOA) were included. Pain, function, and hip extensor strength were evaluated using Visual Analogue Scale, Western Ontario and McMaster Universities Osteoarthritis Index and modified sphygmomanometer respectively; radiographic severity was graded by Kellgren-Lawrence system. Between-group differences were analyzed using the Mann-Whitney U test, associations by Spearman's correlation, and multiple linear regression adjusted for age, gender, and BMI. Symptomatic participants demonstrated significantly lower bilateral hip extensor strength than asymptomatic subjects ( P < 0.001). Lower strength was associated with greater pain, poorer function, and higher Kellgren-Lawrence grades ( P < 0.05). Strength reductions were more pronounced in females across radiographic grades. After adjustment, age and gender were significantly associated with strength in the asymptomatic group, whereas only gender remained significant in the symptomatic group. These findings highlight hip extensor strength as a clinically relevant yet underemphasized factor associated with symptom and structural severity in KOA. Targeted strengthening warrants exploration as a rehabilitation component; however, causality cannot be inferred from this cross-sectional design, and longitudinal studies are needed to establish its effect on clinical or structural outcomes.