Limb-specific associations of isokinetic trunk and knee strength with single-leg hop performance following traumatic knee injury

The single-leg hop distance test (SLHD) is widely used to assess functional performance following knee injury; however, the relative contributions of trunk strength, knee strength, and dynamic balance to hop performance remain unclear. Nineteen individuals with a history of traumatic knee injury (age = 27.9 ± 7.0 years) participated in this study. SLHD, dynamic balance using the Y-Balance Test, and concentric isokinetic trunk and knee flexion–extension strength at 60°/s were assessed bilaterally. Pearson correlation and multiple linear regression analyses were performed separately for injured and non-injured limbs to identify factors associated with SLHD. In the non-injured limb, trunk extension strength (B=0.119, 95% CI: 0.028–0.210, β = 0.393, p = 0.014) and posterolateral balance (B=1.340, 95% CI: 0.698–1.983, β = 0.627, p < 0.001) were associated with SLHD and were retained in the final model, explaining 72% of the variance in SLHD (R² = 0.715, adjusted R² = 0.680, F(2,16) = 20.083, p < 0.001). In the injured limb, knee extension strength (B=0.329, 95% CI: 0.095–0.563, β = 0.478, p = 0.009) and posterolateral balance (B=1.022, 95% CI: 0.312–1.732, β = 0.490, p = 0.008) were associated with SLHD and were retained in the final model, accounting for 65% of the variance (R² = 0.649, adjusted R² = 0.605, F(2,16) = 14.782, p = 0.003). The factors associated with SLHD differed between the injured and non-injured limbs following traumatic knee injury. Knee extension strength and posterolateral balance were associated with SLHD in the injured limb, whereas trunk extension strength and posterolateral balance were associated with SLHD in the non-injured limb.