Prevalence of Postoperative Knee Pain After ACL Reconstruction at 2, 6, and 10 Years of Follow-up: Data From the MOON Group.

BACKGROUND

Persistent knee pain can develop after anterior cruciate ligament injury with subsequent anterior cruciate ligament reconstruction (ACLR) despite a functionally intact graft.

PURPOSE: To identify the prevalence of clinically significant knee pain in patients at 2, 6, and 10 years after ACLR.

STUDY

DESIGN

Cohort study; Level of evidence, 2.

METHODS

3272 patients were enrolled into the Multicenter Orthopaedic Outcomes Network (MOON) between 2002 and 2008 across 7 centers. Each patient completed a questionnaire at baseline that included demographic characteristics, injury factors, participation in sports, and validated outcome measures including the Knee injury and Osteoarthritis Outcome Score (KOOS) pain subscale (scored 0-100 with higher scores signifying less pain). Each patient completed the questionnaire again at 2, 6, and 10 years postoperatively. Three different criteria were used to define clinically significant knee pain: KOOS pain ≤70 points, KOOS pain ≤80 points, or responding "moderate,""severe," or "extreme" to a KOOS pain question.

RESULTS

Median age in the cohort was 23 years (interquartile range, 17-27 years) at the time of enrollment, and 44% of patients were female. A total of 2798 patients (85%) responded to the questionnaire at 2 years postoperatively, with 2759 (84%) responding at 6 years and 2526 (77%) at 10 years. The prevalence of those with KOOS pain ≤70 was 9.3%, 9.0%, and 9.1% at 2, 6, and 10 years after surgery, respectively. The prevalence of KOOS pain ≤80 was 16.6%, 16.3%, and 15.7% at each timepoint, respectively. When a KOOS pain response of "moderate,""severe," or "extreme" was used, the prevalence was 26.3%, 22.9%, and 22.6% at 2, 6, and 10 years, respectively. Interestingly, very few patients had persistent pain at all 3 follow-up points: 48 (1.6%) reported a KOOS pain score ≤70 points, 103 (3.5%) reported a KOOS pain score ≤80 points, and 161 (5.6%) reported moderate or severe pain.

CONCLUSION

The prevalence of clinically significant postoperative knee pain after ACLR was up to 26% at 2 years postoperatively, a percentage that remained unchanged or slightly decreased at 6- and 10-year follow-up. Despite this finding, it was uncommon for individual patients to report clinically significant knee pain at multiple follow-up timepoints.