Muscle Weakness, Proprioceptive Deficits, and Postural Stability in Unilateral Knee Osteoarthritis: A Comparative Analysis of Affected and Unaffected Limbs

Objective: This study aimed to investigate quadriceps and hamstring muscle strength, postural stability, proprioceptive sense, and weight-bearing asymmetry between the affected and unaffected lower limbs in patients with unilateral knee osteoarthritis (OA). Materials and Methods: A total of 79 patients (70 women, nine men; mean age 61.08 ± 6.28 years) diagnosed with unilateral knee OA according to the Kellgren-Lawrence classification were included. Demographic and clinical characteristics were recorded. Pain intensity was assessed using the Visual Analog Scale, and functional status was evaluated with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Muscle strength was measured with a manual muscle dynamometer, proprioception with joint position sense tests at different knee flexion angles, and postural stability using a force platform under both eyes-open and eyes-closed conditions. Weight-bearing distribution during bilateral stance was also evaluated. Results: Quadriceps and hamstring strength were significantly lower in the affected limb compared to the unaffected side (p  0.001). Weight-bearing on the affected limb was reduced under both eyes-open and eyes-closed conditions (p  0.001). However, no significant interlimb differences were observed in postural stability parameters or proprioceptive accuracy at any tested angles (p > 0.05). Additionally, patients demonstrated a significant asymmetry in load transfer during bilateral stance, favoring the non-affected limb. Conclusion: Patients with unilateral knee OA exhibit reduced muscle strength and weight-bearing capacity in the affected limb, along with asymmetrical load distribution during stance. These findings highlight the importance of addressing weight-bearing asymmetry and muscle weakness in early rehabilitation programs to prevent further functional deterioration and disease progression.