Impact of Knee Injury and Disease on Hamstring Steadiness and Strength

Knee instability, which is a major pathogenic factor in musculoskeletal injury (ACL-R) and disease (OA), may stem from decrements (i.e., imbalance, tightness, and/or weakness) of the thigh musculature, particularly hamstrings. However, it is unknown if ACL-R and OA individuals exhibit weaker, less steady hamstring contraction. This study evaluated the magnitude and steadiness of hamstring contraction for individuals with ACL-R and knee OA. We hypothesize that both ACL-R and OA individuals will exhibit weaker and less steady hamstring contractions compared to healthy control individuals. Ten ACL-R and eight knee OA, and sex and age-matched controls (10 and nine, respectively) performed a five second isometric knee flexion contraction. Then, hamstring strength (maximal contraction) and steadiness (PPF and CV) was evaluated and submitted to statistical analysis. We expect ACL-R and OA individuals to exhibit a significant reduction in maximal hamstring strength as less steady (i.e., lower PPF) and more variable (i.e, greater CV) hamstring contraction compared to healthy individuals. Practitioners may need to improve magnitude and steadiness of hamstring contraction to effectively prevent knee musculoskeletal injury and disease.