Meniscal Tear

The menisci are fibrocartilage wedges that transmit 50 to 70% of load across the knee and aid stability and lubrication. Incidence is 60 to 70 per 100,000 a year, and the medial meniscus is torn more often than the lateral.

Tear patterns: longitudinal, bucket handle, radial, horizontal cleavage, flap, complex and root tears. Vascularity defines healing: red-red zone (outer 3 mm, good healing), red-white and white-white (poor). Two groups present:

• Traumatic tears in young athletes (twisting injury), often with anterior cruciate rupture (lateral tears more common acutely)
• Degenerative tears over age 40 with minor trauma, in which MRI shows tears in about a third of asymptomatic people over 50

Root tears behave like a total meniscectomy and drive rapid arthritis. Each partial meniscectomy raises contact pressure and the long term risk of osteoarthritis.

• Joint line pain, delayed effusion (over 12 to 24 hours), catching, clicking and giving way
• Mechanical locking in a bucket handle tear (inability to fully extend)
• Joint line tenderness, McMurray test (pain or click with flexion and rotation), Thessaly test (sensitivity near 90%) and an extension block
• Red flags: a locked knee, hemarthrosis (suggests cruciate tear), inflamed hot knee, and an adolescent with a discoid meniscus

• Clinical examination with joint line tenderness and provocative tests.
• Weight bearing radiographs (including a flexed posteroanterior view) to look for joint space narrowing.
• MRI (sensitivity about 90%) to classify tear type, zone, root involvement and associated cartilage and ligament injury.
• Arthroscopy is diagnostic only when MRI is equivocal and symptoms are disabling.

Differentials: osteoarthritis, anterior cruciate tear, loose body, plica syndrome, patellofemoral pain, medial plateau stress fracture, osteonecrosis.

Degenerative tears without locking: exercise therapy for 12 weeks (strength and neuromuscular training), weight loss, naproxen 500 mg orally twice daily with food for up to 2 weeks, and triamcinolone 40 mg intra articularly once for a flare. Surgery gives no better outcome in most.

Surgery:

• Locked knee with a displaced bucket handle tear: arthroscopy within 1 to 2 weeks, ideally with repair.
• Repair for traumatic tears in the outer zone, ideally under age 40 (inside out, outside in or all-in sutures with a vertical mattress pattern). Rehabilitation: protected weight bearing and motion limited for 6 weeks, return to sport at 4 to 6 months. Failure rate 10 to 25%.
• Partial meniscectomy for irreparable symptomatic tears, preserving as much meniscus as possible.
• Root tear repair by transtibial pullout suture.
• Cefazolin 2 g IV before incision.
• Complications: infection (under 0.5%), venous thromboembolism, saphenous nerve injury, repair failure, arthritis progression.

Follow up at 2 weeks, 6 weeks, 3 months and 6 months. Counsel on activity modification and long term arthritis risk.