Joint Space Loss after Arthroscopic Partial Meniscectomy: Data from the Osteoarthritis Initiative

OBJECTIVES: Knee osteoarthritis (OA) is a prevalent disease that causes substantial disability and use of medical resources, and knee arthroscopy is frequently performed in patients with OA or at risk of developing OA. While meniscectomy has been associated with progression of OA in multiple studies, none have assessed progression of joint space width (JSW) loss compared to matched controls. The Osteoarthritis Initiative (OAI) provides a unique cohort to enable this evaluation. We hypothesize that JSW significantly decreases in meniscectomy patients versus matched controls within a one-year period, and that joint space loss continues to be more rapid in subsequent years. METHODS: A prospective cohort study with matching was conducted using records from the OAI public use data sets. The cohort (n=4796) is contains the incidence subcohort (normal radiographs with risk of developing OA) and the progression subcohort (radiographic evidence of OA). Subjects have fixed-flexion radiographs taken at yearly intervals and validated measurements of JSW are performed. Additional details about the OAI and study design are publicly accessible at http://oai.epi-ucsf.org/datarelease/About.asp. 141 meniscectomy knees were identified and 141 controls were randomly selected while matching for subcohort, gender, study site, age, knee side, and year. Paired t-test was used to evaluate change in JSW over the first year in the 141 matched pairs. Repeated measures MANOVA with adjustment for age, gender, race, and BMI was used to assess longitudinal changes in JSW in a subset of 33 matched pairs with 4 years of JSW measurements available. RESULTS: Meniscectomy and control groups were balanced with respect to age, gender, race, BMI, and baseline JSW. The JSW decrease overa 1-year period was 0.948 mm in meniscectomy knees and 0.137 mm in controls p<0.0001). Table 1 shows similar results when stratifying by subcohort. In the crude and adjusted analyses of knees with 4 years of follow-up, the rate of JSW loss after the first year was not significantly different between meniscectomy knees and controls as shown in Figure 1. CONCLUSION: Arthroscopic partial meniscectomy is associated with increased loss of JSW during the first year after surgery in knees with OA and knees at risk of developing OA; however, the rate of JSW loss is not accelerated over the next 3 years. Immediate JSW narrowing may occur due to loss of the interposed meniscus, due to morphologic changes such as flattening and extrusion, or due to rapid degeneration of articular cartilage in response to increased tibiofemoral contact stress. Significance among both subcohorts suggests that meniscectomy causes progression of osteoarthritis independent of disease stage. Future investigation of change in cartilage and meniscal volumes on MR imaging may further explain the cause of this joint space loss.