Worsening of Radiographic Knee Osteoarthritis Following Medial Meniscus Root Tears and Non-Root Tears
Authors: Chambers Caitlin C. , Lynch John A. , Feeley Brian T. , Nevitt Michael C. 
Published: July 2019

Objectives: Medial meniscus root tear has an established association with knee osteoarthritis (OA), but little is known about the time course of cartilage breakdown or the severity of cartilage damage when compared to meniscal tears which spare the root. The aims of this study were to compare early progressive radiographic degenerative changes in knees with medial meniscus root tears (RT) and medial meniscus tears sparing the root (non-root tears: NRT), and identify risk factors for osteoarthritic progression among patients with RT. Methods: A convenience sample of 3,121 knees from 2,656 participants was drawn from the NIH-funded multicenter Osteoarthritis Initiative (OAI) database. All knees with medial meniscus RT or NRT seen on initial baseline MRI (prevalent) or on subsequent visit MRI (incident) were included. Demographics including sex, age, body mass index (BMI), activity level, knee injury, and knee pain were recorded at index visit (visit at which meniscal injury was first seen) and compared between prevalent RT versus NRT and incident RT versus NRT groups. Radiographic OA worsening was defined as an increase in Kellgren-Lawrence Grade (KLG) at any time from the last normal MRI 12 months before meniscal tear diagnosis (T-12, available in incident tears only) to the index visit (T0), to follow-up MRI 12 months after meniscal tear diagnosis (T+12). Additionally, characteristics of RT patients with OA worsening were compared to those who did not have progressive degenerative changes. Continuous variables were compared using a student’s t-test. Categorical data were compared using Fisher’s exact and chi-squared tests. Results: Within the OAI database, 78 medial meniscus RTs (45 prevalent, 33 incident) were identified, along with 1,030 medial meniscus NRTs (775 prevalent, 255 incident). 75% of incident RTs and 40.9% of incident NRTs (p<0.0001) demonstrated radiographic OA worsening in the 24 months studied, most often concurrent with the medial meniscus root tear, progressing between the last pre-injury MRI (T-12) and the index visit (T0) (Figure 1). As compared to incident NRT, patients with incident RT were more often female, heavier, had a higher activity level, a history of knee injury, and a higher KLG (table 1). Prevalent RT and NRT groups were similar in demographics and rates of radiographic OA worsening. Demographics of patients with incident RT that underwent radiographic OA progression versus those which did not progress were similar with no significant difference in sex, age, BMI, activity level, or history of knee injury and frequent knee pain. The OA progression knees were significantly more likely to have KLG of 0 -1 on pre-RT radiographs than the group that did not progress (66.7% versus 12.5%, p=0.01). Conclusion: For participants with incident medial meniscus tear during the 4-years of OAI, RTs were associated with significantly more progression of radiographic OA than NRTs. A majority of individuals with RTs deny a severe knee injury in the twelve months preceding MRI diagnosis the tear. Compared to incident NRTs, incident RTs were significantly more likely to occur in overweight and more active women, in knees with more severe radiographic OA, and had substantially worse radiographic outcome. Knees which demonstrated radiographic OA progression after incident RT were more likely to have a normal baseline KLG than those which did not progress, but otherwise there were no significant demographic predictors of OA worsening following RT. [Table: see text][Figure: see text]