Development of OA Following ACL Reconstruction: Unexpected Finding in Medial Versus Lateral Meniscus Pathology

OBJECTIVES: Recent studies have described increased risk of OA following ACL reconstruction (ACLR). Systematic reviews have suggested that meniscal pathology, which occurs in up to 60% of patients with ACL injury, increases this risk. The literature reports a 50% incidence of OA following medial meniscectomy, two times the risk compared to lateral meniscectomy. The purpose of this study was to determine the influence of meniscal pathology on the incidence of OA following ACLR. METHODS: All patients who underwent primary autograft or allograft BPTB transtibial ACLR by a single surgeon between 1999-2015 were identified. Revision ACLR, multi-ligamentous reconstructions, and patients with less than 2-year imaging follow-up were excluded. Meniscus pathology and treatment were recorded. OA was defined at follow-up as Kellgren-Lawrence grade III-IV on plain radiographs. Chi-square tests assessed differences in incidence rates (p<0.05). RESULTS: A consecutive series of 103 patients (56 males, 47 females; age 36.1±11.4 years) with BPTB ACLR with an average follow-up of 8.81±4.96 (range 2-20 years) were included. The prevalence of medial meniscus tears at the time of ACL injury was 47.6% (49/103) and prevalence of lateral meniscus tears was 56.3% (58/103) (p=0.166). Medial compartment OA was seen in 9.7% (10/103) of patients. Prevalence of medial compartment OA was greater in patients with medial meniscus tear (14.3%; 7/49) compared to those without a medial meniscus tear (5.6%; 3/54); however, this was not significant (p=0.135). Of the 7 patients with medial meniscal tear and medial compartment OA, 5 underwent partial medial meniscectomy and 2 underwent repair. Lateral compartment OA was seen in 14.6% (15/103). The prevalence of lateral compartment OA was greater in patients with a lateral meniscus tear (22.4%; 13/58) compared to patients without lateral meniscus tears (4.4%; 2/45) (p=0.01). Patients with lateral meniscus tear were 5.04 [95%CI: 1.2 to 21.2] times more likely to develop OA. Thirteen of the 47 (28%) patients that underwent partial lateral meniscectomy developed lateral OA compared to 0% of patients (0/10) that underwent lateral meniscal repair (p=0.068). CONCLUSION: While studies with multiple surgeons and rehabilitation protocols have shown the development of OA following ACLR is increased with medial meniscal pathology, we found that the prevalence of medial OA was not significantly higher in these patients with medial meniscal tear at an average of 8.81 years follow-up. Whereas, lateral meniscal repair dramatically reduced the development of knee OA compared to partial meniscectomy in this cohort of patients with ACLR. These findings can inform clinical practice as despite prior literature indicating a relationship between medial meniscal tear and osteoarthritis, we did not see a greater prevalence of OA amongst patients undergoing ACLR with a medial meniscal tear. Further, a lateral meniscal repair offers superior protection against OA when compared to partial lateral meniscectomy in treating lateral meniscal tears and is essential in the treatment of these complex patients.