MENISCAL TEARS

MENISCAL TEARS

STRUCTURE OF THE MENISCUS
• Medial is semicircular • Moves 2-5 mm through full ROM • Lack of motion may promote tears • Fibers from the deep medial collateral • Covers 60% of articular cartilage • Lateral almost a complete circle • Moves ~1 cm through full ROM • Both made of fibrocartilage
TEARS AND ZONES
STRUCTURE OF THE MENISCI
• Vascular supply good in the most peripheral 20% of the fibers • Supplied by the geniculate arteries • Inner 1/3 of the ring is avascular • Relatively thin • Nourished through synovial fluid • Middle 1/3 of the ring is combination
FUNCTION OF THE MENISCI
• Distribute load across the knee joint • 2-4x body weight during walking • 6-8x body weight during running
• Menisci deepen the socket of the tibial plateau, contributing to stability • Wedge shape limits translation of femur on tibial plateau
PATHOPHYSIOLOGY
• In acute knee injuries with ACL intact, medial meniscal injury is 5 times more likely than lateral • In acute knee injuries with ACL ruptured, lateral meniscus more likely to be involved
HISTORY: THE KEY TO DIAGNOSIS
• Twisting on planted foot • Inertial forces or external forces • Acute effusion in acute injury • Waxing and waning course with pain and effusion intermittently in chronic injury • Locking or popping of knee, especially if followed by effusion
IS THERE EFFUSION?
MCMURRAY’S TEST
APLEY’S TEST
VALUE OF MRI AS DIAGNOSTIC TOOL• Studies do NOT prove it superior to composite clinical exam • Many false positives appear
TREATMENT OPTIONS
• Total meniscectomy • Partial meniscectomy • Meniscal repair • Inside out • Outside in • All inside • Conservative (No operative intervention)
CONSEQUENCES OF MENISCECTOMY
• As early as 1948 Fairbanks noted increased osteophyte formation and femoral cartilage deterioration in meniscectomized knees • Total meniscectomy remained a common procedure until the 1980’s • In medial meniscectomy, load bearing surfaces are halved, doubling stress on tibial plateau • If 15-30% of meniscus is removed, forces between tibia and femur increase up to 350%
BUCKET HANDLE TEAR