Magnetic resonance imaging and arthroscopic findings of the popliteomeniscal fascicles with and without recurrent subluxation of the lateral meniscus.

PURPOSE: The aim of this study was to examine the posterosuperior popliteomeniscal fascicle (sPMF) and anteroinferior popliteomeniscal fascicle (iPMF) by use of magnetic resonance imaging in control knee joints and joints with recurrent subluxation of the lateral meniscus (RSLM) to determine the incidence of abnormal popliteomeniscal fascicles (PMFs) in these groups.

METHODS

Knee joints were diagnosed with RSLM when there was a history of mechanical locking episodes and when subluxation of the lateral meniscus was recognized on arthroscopy. In this study 238 knee joints were evaluated. The joints were classified into a control group (215 joints), RSLM group (16 joints), and contralateral RSLM group (7 joints). Classification of the sPMF (iPMF) on magnetic resonance imaging was as follows: type I, a tense, low-intensity band ran from the superior (inferior) border of the lateral meniscus to the popliteus tendon; type II, an unclear band ran from the superior (inferior) border of the lateral meniscus; and type III, no band was observed. Types II and III were thought to exhibit abnormal PMFs. The distribution of knee joints among the 3 groups and PMF types was examined.

RESULTS

Percentages of abnormal sPMFs and iPMFs were 40% and 26%, respectively, in the control group; 100% and 29%, respectively, in the contralateral RSLM group; and 100% and 100%, respectively, in the RSLM group. A significant difference in the distribution of knee joints by classification of sPMFs was recognized between the control and contralateral RSLM groups (P < .0001). A significant difference in iPMFs was also recognized between the contralateral RSLM and RSLM groups (P = .0005).

CONCLUSIONS

A significantly high incidence of abnormal sPMFs was found in RSLM and contralateral knees. Thus abnormal sPMFs existed in both knee joints before patients had locking symptoms, suggesting that abnormal sPMFs may be required for locking symptoms. A significantly high incidence of abnormal iPMFs was found only in the knee joints with RSLM. An abnormal iPMF is thus the essential lesion to allow the at-risk lateral meniscus to become unstable beyond the rate of control knees.

LEVEL OF EVIDENCE: Level III, case-control study.