Clinical and radiographic results of arthroscopic partial lateral meniscectomies in stable knees with a minimum follow up of 20 years.

PURPOSE: The purpose of this retrospective multicentric study was to evaluate the long-term effects of lateral meniscectomy and to identify those patients who are at the most risk of developing osteoarthritis (OA). METHODS: Eighty-nine arthroscopic partial lateral meniscectomies in stable knees with a mean follow-up of 22 +/- 3 years were included. The following influencing factors were analyzed: age, sex, body mass index (BMI), physical activity, alignment, the types of meniscal lesions, the extent of meniscal resections and the initially associated cartilage lesions. An independent examiner reviewed all patients, using subjective (KOOS and IKDC scores) and objective clinical and radiological evaluations (IKDC score). The contralateral knee was used as a reference to calculate the prevalence and the incidence of OA. RESULTS: The mean age at the time of surgery was 35 +/- 13 years. The main location of the lesions was the mid-section of the lateral meniscus (79 % of the cases). At the latest follow-up, 48 % of the patients had an active lifestyle with as many as 48 % of the patients enjoying moderate to intense physical activity 22 years after the procedure (vs. 71 % before surgery). The KOOS score evolved from 82 to 69 % during the same period. The prevalence of OA was 56 % in the affected knee and the difference of prevalence between the operated and healthy knees was 44 %. In those patients presenting with an OA of the operated knee and a normal contralateral knee, the incidence of OA was 53 %. Predictors of OA were an age superior to 38 years at the time of surgery, obesity (BMI >30), and valgus malalignment as well as the presence of cartilage and degenerative meniscal lesions at the time of surgery. CONCLUSION: In the long term, arthroscopic partial lateral meniscectomy in stable knees without initial cartilage lesions might yield good to excellent results in young patients. Patients are at higher risk to develop symptomatic OA if they are over 40, having a high BMI, valgus malalignment and cartilage lesions at the time of surgery. This study provides precise guidelines for the surgical treatment of lateral meniscus tears. LEVEL OF EVIDENCE: IV.