Subcortical Bone Cysts at the Medial Meniscus Posterior Root Are Associated with Longer Symptom Duration but Not with...

Background and Objectives: Subcortical bone cysts at the tibial attachment of the medial meniscus posterior root (MMPR) may reflect chronic degenerative changes; however, their clinical significance in medial meniscus posterior root tear (MMPRT) remains unclear. This study assessed whether bone cysts are associated with symptom duration and whether their presence influences healing status or medial meniscus extrusion (MME) after transtibial pullout repair (TPR). Materials and Methods: Seventy-four consecutive patients who underwent arthroscopic TPR for MMPRT between January 2022 and December 2024 were retrospectively reviewed. After applying exclusion criteria, 50 patients were included and divided into cyst-positive (n = 20) and cyst-negative (n = 30) groups based on preoperative MRI findings. Clinical outcomes, MME, and second-look arthroscopic healing status at 6 months postoperatively were compared between groups. Multivariable linear regression analysis was performed to identify independent predictors of postoperative MME. Results: The cyst-positive group had significantly longer symptom duration than the cyst-negative group (13.8 ± 3.0 vs. 8.8 ± 2.8 weeks, p < 0.001) and demonstrated higher grades of MMPR degeneration (p < 0.05). Complete healing was observed in 60.0% of patients in each group, and no failed healing cases were noted. Postoperative MME at 6 months was comparable between groups (3.8 ± 0.8 vs. 3.8 ± 1.0 mm). Multivariable regression analysis identified baseline MME as the strongest independent predictor of postoperative MME (β = 0.67, p < 0.001), whereas bone cyst presence was not independently associated with postoperative extrusion. Conclusions: Subcortical bone cysts at the MMPR attachment are associated with longer symptom duration and more advanced root degeneration. However, their presence was not significantly associated with healing status or postoperative MME after MMPRT repair. These findings suggest that bone cyst formation may be associated with chronic degenerative changes at the root attachment, but should not discourage surgeons from performing root repair.