MENISCAL TEARS.docx

Structure of the meniscus Medial meniscus is semicircular. The medial meniscus is less mobile than the lateral and, consequently, the medial meniscus is more liable to tearing when subjected to abnormal stresses. Lateral meniscus almost a complete circle Moves ~1 cm through full ROM. Both are made...

Structure of the meniscus Medial meniscus is semicircular. The medial meniscus is less mobile than the lateral and, consequently, the medial meniscus is more liable to tearing when subjected to abnormal stresses. Lateral meniscus almost a complete circle Moves ~1 cm through full ROM. Both are made of fibrocartilage. Vascular supply good in the most peripheral 20% of the fibers. Supplied by the geniculate arteries. The inner 1/3 of the ring is avascular. Relatively thin. Nourished through synovial fluid. The middle 1/3 of the ring is a combination. Function of the menisci Distribute load across the knee joint. 2-4x body weight during walking. 6-8x body weight during running. Menisci deepens 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 is more likely to be involved. Types of meniscal tear Grinding forces split the fibers of the meniscus. If the separated fragment remains attached at the front and back, the lesion is called a bucket-handle tear. If the tear emerges at the free edge of the meniscus, it leaves a tongue based anteriorly (an anterior horn tear) or posteriorly (a posterior horn tear). Diagnosis History is the key to diagnosis. Twisting on planted foot. Waxing and waning course with pain and effusion intermittently in chronic injury. Locking or popping of knee, especially if followed by effusion. Examination Check if there is effusion by Ballottement test. McMurray’s test. Apley’s test. Investigations MRI: Studies do NOT prove it superior to composite clinical exam. Many false positives appear. Treatment Conservative Not an option if knee locked, fragment not reduced. Symptom relief with NSAIDS, immobilization. Physical therapy focuses on closed chain exercise of quadriceps and hamstrings. Operative Include (1) total meniscectomy, (2) partial meniscectomy, (3) meniscal repair. All these procedures are best done by arthroscopy. Criteria for meniscal repair or Partial meniscectomy Criterion Repair Partial meniscectomy Distance from rim Less than 3 mm. More than 3 mm Mobility of fragment Stable Mobile Age of injury Recent Old Return To play Later Sooner Age of patient Younger Older