Non-operative management of medial meniscus posterior horn root tears is associated with worsening arthritis and poor clinical outcome at 5-year follow-up

PURPOSE: Medial meniscus posterior root tears (MMPRTs) are a significant source of pain and dysfunction, but little is known about the natural history and outcome and for non-operative management of these lesions. The purpose of this study was to evaluate (1) the mid-term clinical and radiographic outcomes of non-operative treatment of MMPRTs and (2) risk factors for worse outcomes. METHODS: A retrospective review was performed for patients with symptomatic, unrepaired MMPRTs and a minimum 2-year follow-up for IKDC and Tegner outcome scores. Baseline and final radiographs were reviewed and graded according to Kellgren-Lawrence scores. Baseline MRIs were reviewed for the presence of meniscal extrusion, subchondral oedema, and insufficiency fractures. Failure was defined as conversion to arthroplasty or severely abnormal patient subjective IKDC score. RESULTS: Fifty-two patients (21M:31F) with a mean age of 58 ± 10 years were diagnosed with symptomatic MMPRTs clinically and confirmed by MRI and followed for a mean of 62 ± 30 months. Sixteen patients (31 %) underwent total knee arthroplasty at a mean of 30 ± 32 months after diagnosis with higher Kellgren-Lawrence grades associated with increased rates of arthroplasty (p = 0.01). Mean IKDC scores for the remaining patients were 61.2 ± 21 with significantly lower scores in females compared to males (75 ± 12 vs. 49 ± 20; p = 0.03). Mean Kellgren-Lawrence grades and rates of arthritis progressed over time on radiographs (1.5 ± 0.7 vs. 2.4 ± 1.0; p < 0.001 and 78 % vs. 51 %; p = 0.01). Overall, 87 % of patients failed non-operative treatment. CONCLUSIONS: Non-operative treatment of medial meniscus posterior horn root tears is associated with poor clinical outcome, worsening arthritis, and a relatively high rate of arthroplasty at 5-year follow-up. Female gender was associated with lower subjective scores and higher rate of arthroplasty. The current study provides a natural history benchmark for clinical outcomes that can be expected in patients with medial meniscus posterior horn root tears undergoing non-operative treatment and helps in counselling patients with these types of injuries. LEVEL OF EVIDENCE: IV.