Quadriceps Function, Knee Pain, and Self-Reported Outcomes in Patients With Anterior Cruciate Ligament Reconstruction

Context: Interactions among muscle strength, pain, and self-reported outcomes in patients with anterior cruciate ligament reconstruction (ACLR) are not well understood. Clarifying these interactions is of clinical importance because improving physical and psychological function is thought to optimize outcomes after ACLR. Objective: To examine the relationships among neuromuscular quadriceps function, pain, self-reported knee function, readiness to return to activity, and emotional response to injury both before and after ACLR. Design: Descriptive laboratory study. Patients or Other Participants: Twenty patients (11 females and 9 males; age = 20.9 +/- 4.4 years, height = 172.4 +/- 7.5 cm, weight = 76.2 +/- 11.8 kg) who were scheduled to undergo unilateral ACLR. Main Outcome Measure(s): Quadriceps strength, voluntary activation, and pain were measured at presurgery and return to activity, quantified using maximal voluntary isometric contractions (MVICs), central activation ratio, and the Knee Injury and Osteoarthritis Outcome Score pain subscale, respectively. Self-reported knee function, readiness to return to activity, and emotional responses to injury were evaluated at return to activity using the International Knee Documentation Committee questionnaire (IKDC), ACL Return to Sport After Injury scale (ACLRSI), and Psychological Response to Sport Injury Inventory (PRSII), respectively. Pearson product moment correlations and linear regressions were performed using raw values and percentage change scores. Results: Presurgical levels of pain significantly predicted 31% of the variance in the ACL-RSI and 29% in the PRSII scores at return to activity. The MVIC and pain collected at return to activity significantly predicted 74% of the variance in the IKDC, whereas only MVIC significantly predicted 36% of the variance in the ACL-RSI and 39% in the PRSII scores. Greater increases in MVIC from presurgery to return to activity significantly predicted 49% of the variance in the ACL-RSI and 59% of the variance in the IKDC scores. Conclusion: Decreased quadriceps strength and higher levels of pain were associated with psychological responses in patients with ACLR. A comprehensive approach using traditional rehabilitation that includes attention to psychological barriers may be an effective strategy to improve outcomes in ACLR patients.