Abstract
Objectives:
ACL reconstruction (ACLR) can restore knee stability and return athletes to the field of play, but these athletes are still at risk of knee pain from post-traumatic osteoarthritis. The purpose of this study was to determine the incidence of clinically significant knee pain at 2, 6 and 10 years after ACLR in patients who had surgery using modern surgical techniques and rehabilitation protocols including early motion.
Methods:
The Multicenter Orthopaedic Outcomes Network (MOON) enrolled 3273 patients at 7 centers between 2002 and 2008. Patients completed a baseline questionnaire including demographics, injury characteristics, sports participation, and validated outcome instruments including KOOS, IKDC, and Marx Activity. Surgeons completed a questionnaire documenting physical examination, arthroscopic findings, and details of the procedure. Patients repeated the questionnaire at 2, 6 and 10 years. Patients were categorized into symptomatic versus asymptomatic at each timepoint by multiple criteria: KOOS pain <=70, KOOS pain <= 80, or answering “moderate, severe, or extreme” to any KOOS pain question (a common entry criteria for OA clinical trials). We hypothesized that incidence of knee pain would increase with increasing time since surgery. We applied McNemar’s test with a significance level of p<.05.
Results:
The median age of the cohort was 23 years (IQR 17-27) and 44 percent were female. 2798 completed the questionnaire at 2 years (85%), 2759 at 6 years (84%), and 2526 at 10 years (77%). For the 70-point cutoff, the incidence of clinically significant knee pain was 9.3% at 2 years, 8.9% at 6 years, and 9.1% at 10 years. For the 80-point cutoff, the incidence was 16.6% at 2 years, 16.3% at 6 years, and 15.7% at 10 years. For the “moderate, severe or extreme” criteria, the incidence was 26.3% at 2 years, 22.9% at 6 years, and 22.6% at 10 years. There were no statistically significant differences between the three timepoints for any of the criteria.
Conclusions:
A substantial proportion of patients develop clinically significant knee pain as early as 2 years after ACLR (as high as 26.3% by one criteria); however, this proportion remains constant at 6 and 10 years after surgery. We expected an increased proportion of patients with symptoms of PTOA by 10 years post-op; however, these findings suggest that the development of knee pain occurs early after ACLR, and that treatments should be focused on improving recovery and minimizing knee pain early to prevent symptoms of PTOA in the first 10 years after surgery.