A new arthroscopic classification of degenerative medial meniscus root tear that correlates with meniscus extrusion on magnetic resonance imaging.
BACKGROUND
To determine a new classification system for medial meniscus root tears (MMRT) based on arthroscopic findings.


METHODS
24 knees (55%) belonged to the nondisplaced or overlapped group, and 20 knees (45%) to the widely displaced group. Absolute meniscal extrusion was defined as distance between outer edge of the articular cartilage of tibial plateau and meniscal outer edge. Relative extrusion was defined as extruded meniscus width divided by entire meniscal width, multiplied by 100. The proportion of knees with major (>3 mm) extrusion were compared in two groups, as were the severity of chondral wear and osteoarthritic change.


RESULTS
Absolute (4.6 mm vs. 3.7 mm, P=0.006) and relative (46% vs. 39%, P=0.042) extrusion of the medial meniscus were greater in widely displaced than in nondisplaced or overlapped group. Medial joint space width was significantly narrower in the widely displaced than in the nondisplaced or overlapped group (3.0 mm vs. 4.0 mm, P=0.007). The widely displaced group had a 4° greater varus deformity, and higher rates of major extrusion (>3 mm), grade III or IV chondral wear in the medial femoral condyle (60% vs. 29%, P=0.039) and medial compartment osteoarthritis (75% vs. 21%, P=0.001) than did the nondisplaced or overlapped group.


CONCLUSIONS
Widely displaced MMRT had greater meniscal extrusion and more severe chondral wear and osteoarthritis than did nondisplaced or overlapped MMRT. In this novel classification system, the stage of MMRT severity was associated with tear site displacement.


LEVEL OF EVIDENCE
Case series (level IV).
['Bin|Seong-Il|SI|', 'Jeong|Tae-Wan|TW|', 'Kim|Su-Jin|SJ|', 'Lee|Dae-Hee|DH|']
D000328:Adult D000368:Aged D001182:Arthroscopy D005260:Female D005500:Follow-Up Studies D006801:Humans D008279:Magnetic Resonance Imaging D008297:Male D008592:Menisci, Tibial D008875:Middle Aged D015203:Reproducibility of Results D012189:Retrospective Studies D012421:Rupture D000070600:Tibial Meniscus Injuries D013997:Time Factors
Medial meniscus Root tear Extrusion Displacement Arthroscopy