Hip Abductor and Adductor Muscles Activity Patterns During Landing After Anterior Cruciate Ligament Injury.

CONTEXT: Hamstring and quadriceps activity adaptations are well known in individuals with anterior cruciate ligament deficiency (ACLD) and reconstructed (ACLR) to potentially compensate for knee joint instability. However, few studies have explored hip muscles activity patterns after ACL injury.

OBJECTIVE: To examine the activation characteristics of gluteus medius (GMED) and adductor longus in ACLR and ACLD subjects compared with controls.

DESIGN: Case-control study.

SETTING: Athletic training room and university lab.

PARTICIPANTS: Twelve healthy and 24 ACL-injured (12 ACLR and 12 ACLD) recreationally active male volunteers.

INTERVENTIONS: Surface electromyography of the GMED and adductor longus were recorded during a single-leg vertical drop landing and normalized to maximum voluntary isometric contractions.

MAIN OUTCOME MEASURES: Preparatory and reactive muscle activity and coactivation were analyzed from 100 milliseconds prior to initial contact to 250 milliseconds postcontact.

RESULTS: During reactive activity, ACL-injured (ACLR and ACLD) participants demonstrated significantly lower peak GMED activity compared with controls (F = 4.33, P = .02). In addition, ACLR participants exhibited significantly lower reactive GMED:adductor longus coactivation muscle activity compared with controls (F = 4.09, P = .03).

CONCLUSION: Our findings suggest neuromuscular adaptations of the hip musculature are present in people at least 2 years from ACL injury. GMED activation exercises should be considered in designing rehabilitation programs for ACL-injured individuals.