Difference in Knee Joint Structure and Lower Extremity Functioning Among People with Varying Severity of Knee Osteoarthritis: A Cross-Sectional Study

Osteoarthritis (OA) is a highly prevalent musculoskeletal condition. It is reported that knee OA progressively affects lower-extremity functioning. Evidence is lacking on when there is a substantial decline in function and whether this trend differs between males and females and disease severity. This study aimed to examine influence of gender and increasing grade of knee OA on lower-extremity function. Following Institutional Ethical Committee approval and signed-informed consent, 115 participants (57-males, 58-females), aged 40-65 years, with diagnosed knee OA (grade 1-4) were recruited. Lower-extremity function was studied using reliable and valid outcome variables such as muscle strength-endurance, joint motion, ground-level activity exposure and physical activity. The medial knee joint space width (JSW) decreased by 56.7%(males) and 49.2%(females) from grades 1 to 2 and by 29.6%(males) and 47.8%(females) from grades 3 to 4. Lower-extremity muscle strength and mobility measured by 30-second-deep-squat test declined by 62%(males) and 40.4%(females) from grades 1 to 2 and by 94.4%(males) and 60.9%(females) from grades 3 to 4. Lower-extremity muscle endurance measured by 30-second-chair-sit-to-stand test declined by 8.3%(males) and 7.1%(females) from grades 1 to 2 and by 31.6%(males) and 85.7%(females) from grades 3 to 4. Physical function decreased by 0.3%(males) and 2.3%(females) from grades 1 to 2 and by 22.7%(males) and 32.0%(females) from grades 3 to 4. Physical activity decreased by 27.6%(males) and 28.6%(females) from grades 1 to 2 and by 53.1%(males) and 60.7%(females) from grades 3 to 4. A substantial decline was observed from grades 3 to 4, when both males and females presented considerable reductions in lower-extremity function.