Description
Objectives
It is well known that medical meniscus extrusion (MME) caused by medial meniscus injury is associated with knee osteoarthritis (OA). For MME, medial collateral ligament (MCL) injuries were considered to be one of the main risk factors, because the deep medial collateral ligament (dMCL) has an important role as a stabilizer for medial meniscus.(Paletta GA et al, OJSM 2020) However, there are no clinical reports which demonstrate the relationship between MME and isolated MCL injury including dMCL injury. Therefore, the purpose of this study was to investigate the incidence of MME in the knee with isolated MCL injury and examine its characteristics.
Methods
Date was prospectively collected over a period of three years from 2018, and 26 patients (23 men and 3 women with a mean age of 31.2±16.7 years) with isolated MCL injury was identified using MRI images which was taken immediately after the injury. Those who had medial meniscus tears were excluded. On MRI, the injury site of MCL (e.g. sMCL or dMCL and femoral or tibial side) was evaluated. MME was also measured as the distance between the peripheral margin of medial meniscus and medial cartilage end of tibial plateau on the coronal image of MRI.
Results
In 26 MCL injuries, there were 15 isolated sMCL, 1 isolated dMCL and 10 combined (both sMCL and dMCL) injuries. Among total 25 sMCL injuries, 20 femoral and 5 tibial sMCL injuries were identified, while, among 11 dMCL injuries, 6 femoral and 5 tibial dMCL injuries were identified.
The average MME was 1.5±1.0mm (0-3.7mm) and there were 4 (15%) patients with three or more millimeters of MME. (Figure 1)
In terms of the relationship between MME and injury site of MCL, patients with three or more millimeters of MME were significantly more associated with deep MCL injury (100%, 4 of 4) than those with <3mm of MME (32%, 7 of 22) (P<0.05) (Table 1). Also, three out of four patients who had both sMCL and dMCL injuries on tibial side showed three or more millimeters of MME. (figure 2)
Conclusions
We have examined the extent of MME in isolated MCL injury using MRI. Of all the patients with isolated MCL injury, we have identified 15% (4 of 25) having three or more millimeters of MME and all the cases had deep MCL injury (100%, 4 of 4). Furthermore, 75% of the patients with both sMCL and dMCL injuries on tibial side had three or more millimeters of MME, which indicates that tibial side of dMCL contributes to meniscal stability. Therefore, attention needs to be paid to those who have deep MCL injury, especially on tibial side, since three or more millimeters of MME are high risks of developing knee OA.
