Five key ultrasound findings associated with medial meniscus posterior root tear

Purpose

Medial meniscus posterior root tear (MMPRT) is a critical condition leading to knee osteoarthritis. Although MRI is the standard diagnostic tool, its availability and cost can be limiting. This study aimed to identify characteristic ultrasound (US) findings of MMPRT and determine the criteria for recommending MRI.

Methods

This multicenter prospective study included 100 patients (101 knees, mean age 58.3 ± 11.2 years, 58 males and 42 females) with medial knee joint pain. All patients underwent US and MRI evaluations. US findings included joint effusion, synovial hypertrophy, and medial meniscus extrusion (MME) in the supine, 90° flexion, and standing positions. Color Doppler evaluation of Doppler signals (DSs) in the bursa and through the femur and tibia were performed. Statistical analysis compared US findings between MMPRT and non-MMPRT groups.

Results

The MMPRT group showed significantly higher rates of joint effusion (p = 0.028) and increased MME in all positions (p < 0.001). MME changed from 0° to 90° knee flexion (p = 0.003). Color Doppler evaluations revealed DSs through the femur (p = 0.008) and tibia (p = 0.013). Horizontal meniscal tears were more frequent in the non-MMPRT group (p < 0.001). For three or more positive parameters, sensitivity and specificity were 80% and 82.7%, respectively.

Conclusion

Five key US findings—joint effusion, increased MME, smaller MME change in knee flexion, fewer horizontal meniscal tears, and increased DSs through the femur and tibia—are characteristic of MMPRT. These suggest that US can effectively identify patients requiring MRI, facilitating early management.