The role of medial meniscus posterior root tear and proximal tibial morphology in the development of spontaneous osteonecrosis and osteoarthritis of the knee.

BACKGROUND: Medial meniscus posterior root tear (MMPRT) has been reported to play a key role in the development of spontaneous osteonecrosis of the knee (SONK) and osteoarthritis (OA) of the knee. However, little is known about the differences in the development of SONK and OA after MMPRT. The purpose of this study was to investigate the factors contributing to the development of these conditions.

METHODS: We evaluated the existence of MMPRT and the extent of medial meniscal extrusion in preoperative magnetic resonance images and proximal tibial morphology in radiographs of 45 patients with SONK and 104 patients with OA who underwent knee surgery.

RESULTS: There were no significant differences in age, gender, height, weight, and body mass index between the two groups. The incidence of MMPRT and the mean posterior tibial slope (PTS) were significantly higher in SONK than in OA patients (62.2% versus 34.3%, P=0.002, and 12.8° versus 10.5°, P<0.001, respectively). The mean extent of meniscal extrusion was larger in OA than in SONK patients (7.5mm versus 5.3mm, P<0.001). The mean tibial varus angle was 4.8° in SONK and 5.4° in OA, with no significant difference between the two (P=0.088). Multivariable logistic regression analysis showed that compared with OA, SONK was more closely associated with the existence of MMPRT and had a smaller extent of medial meniscus extrusion and higher PTS.

CONCLUSION: MMRPT and higher PTS were more closely associated with the development of SONK than with that of OA.