Knee valgus proprioception, muscle activity, patient-reported outcomes and dynamic balance control after anterior cruciate ligament reconstruction: a cross-sectional case–control study

Abstract Background Proprioceptive deficits following anterior cruciate ligament reconstruction (ACLR) are commonly assessed using sagittal-plane, nonweight-bearing tasks that may not reflect the demands of functional activities. This study evaluated the test–retest reliability and discriminative validity of a weight-bearing knee valgus discrimination task (Knee-VEDA) and compared proprioceptive acuity, muscle activity, dynamic balance, and patient-reported outcomes between individuals with ACLR and healthy controls. Methods Sixty-three participants (32 ACLR, 31 controls) performed the Knee-VEDA with concurrent surface electromyography (sEMG) of seven lower-limb muscles. Test–retest reliability was assessed. Dynamic balance and patient-reported outcomes were evaluated using the Y-Balance Test, International Knee Documentation Committee (IKDC) form, and Knee injury and Osteoarthritis Outcome Score (KOOS). Results The Knee-VEDA demonstrated acceptable-to-good test–retest reliability (ACLR ICC = 0.84; controls ICC = 0.64) and acceptable discriminative validity (AUC = 0.835, p < 0.001). The ACLR group exhibited significantly poorer proprioception in the operated limb compared with their intact limb and controls ( p < 0.001). sEMG analysis revealed not statistically significant between-group differences in lower-limb muscle activity. ACLR participants also demonstrated inferior Y-Balance performance compared with controls ( p = 0.02). In the ACLR group, better Knee-VEDA scores correlated with better Y-Balance ( r = 0.50, p < 0.001), and better KOOS symptoms scores ( r = 0.55, p = 0.001). Conclusions The Knee-VEDA may be a useful tool for assessing weight-bearing knee proprioception after ACLR, showing acceptable test–retest reliability and discriminative validity. After ACL reconstruction, operated-limb proprioceptive acuity was found to be reduced during the valgus task. Further validation is needed before clinical application.