Lower Limb Strength Asymmetry is Associated With Stair Ambulatory Pain in Individuals With or at Risk for Knee Osteoarthritis

Objective: To determine whether self-reported pain during stair ambulation was associated with inter-limb strength asymmetry and hamstring-quadriceps ratios (HQR). Design: 4086 participants with or at risk for tibiofemoral knee osteoarthritis were selected from the Osteoarthritis Initiative. Participants were grouped by self-reported pain severity during stair ambulation; right limb pain (RPG), left limb pain (LPG), or equal pain bilaterally (EPG). One-way analyses of covariance tested between-groups differences in knee extensor and flexor strength, symmetry index (SI) and bilateral HQR. Results: RPG participants had significantly lower right knee extensor ( P <0.001) and flexor ( P <0.001) strength, and knee extensor ( P <0.001) and flexor ( P <0.001) SI, compared to the EPG. LPG participants had significantly lower left knee extensor ( P <0.001) and flexor ( P <0.001) strength, and significantly higher extensor ( P <0.001) and flexor ( P <0.001) SI, compared to the EPG. No significant differences in HQR were observed in the RPG ( P =0.820; P =0.743) or LPG ( P =0.11; P =0.601), when compared to the EPG. Conclusion: Self-reported knee pain during stair ambulation was significantly associated with ipsilateral strength deficits and muscle strength asymmetry. These findings suggest that asymmetrical self-reported knee pain may be related to underlying strength imbalances in individuals with knee osteoarthritis and warrant further investigation regarding its potential clinical relevance.