Meniscal Degeneration

Age related structural breakdown of the menisci (fibrocartilage wedges that distribute load across the knee), with horizontal cleavage tears, complex tears, flap tears, and extrusion from the joint margin. It is part of the osteoarthritic process in most patients, and the tears often precede or accompany cartilage loss.

• Prevalence: MRI shows degenerative meniscal tears in about 35% of adults over 50 and in 60% of those with knee osteoarthritis, and in many cases they are asymptomatic. A tear on MRI does not prove it is the source of pain.
• Risk factors: age above 40, obesity, previous knee injury, occupations with kneeling and squatting, malalignment (varus knee), and inflammatory arthritis.
• It differs from traumatic tears (young patients, twisting injury, often repairable), and the two should not be confused.
• Medial meniscus posterior horn is the commonest site of degenerative tears.

• Gradual or insidious medial or lateral joint line pain, worse with twisting, squatting, stairs and prolonged standing, and relieved by rest. Sometimes a minor event (rising from a squat) triggers acute pain.
• Mechanical symptoms: catching, clicking, a sense of giving way and intermittent swelling are common, but true locking (an inability to fully extend the knee) is rare and suggests a displaced flap or bucket handle fragment.
• Examination: joint line tenderness, a small effusion, pain at the end of flexion, and positive joint line pain on McMurray-type twist and Thessaly tests (low specificity in older patients), with normal ligament testing and often features of osteoarthritis (crepitus, bony enlargement and reduced range).
• Differential diagnosis: knee osteoarthritis, subchondral insufficiency fracture or spontaneous osteonecrosis (sudden severe medial pain with a normal X-ray at first), pes anserine bursitis, medial collateral ligament sprain, patellofemoral pain, plica, gout and pseudogout, septic arthritis, referred hip pain and baker cyst.
• Red flags: a locked knee, hot swollen joint with fever, night pain, sudden severe pain with inability to bear weight, and a history of cancer.
• Complications: progression of osteoarthritis (meniscal extrusion above 3 mm is linked to rapid cartilage loss), pain and disability, and loss of function.

• Clinical, with weight bearing X-rays (anteroposterior, lateral, skyline, and posteroanterior flexion views) to assess osteoarthritis, joint space narrowing, alignment and chondrocalcinosis.
• MRI is not needed routinely, because incidental degenerative tears are common. Request it for true locking, suspected subchondral insufficiency fracture, an unexplained effusion, or when surgery is considered. Ultrasound for meniscal extrusion and cysts.
• Blood tests (CRP, ESR, urate) and aspiration of a hot effusion for cell count, crystals and culture when inflammatory or crystal arthritis or infection is possible.

• First line: education, activity modification, weight loss when overweight (a 5 kg loss reduces knee load markedly), and structured exercise (quadriceps, hamstring, hip abductor and core strengthening, with low impact aerobic work, 2 to 3 times weekly for 12 weeks or more), with equal results to arthroscopic surgery in degenerative tears.
• Analgesia:
  • Paracetamol 1 g orally 6 hourly.
  • Topical diclofenac 1% gel 2 to 4 g 3 to 4 times daily.
  • Ibuprofen 400 mg orally 8 hourly with food (or naproxen 500 mg 12 hourly, or celecoxib 200 mg daily) for the shortest effective period, with gastroprotection where needed.
  • Tramadol 50 mg orally 6 to 8 hourly (maximum 400 mg daily) only for short courses.
  • Duloxetine 30 mg daily increasing to 60 mg daily for chronic osteoarthritic pain.
• Supports: a cane in the opposite hand for painful stance, cushioned shoes, and an unloader brace or lateral wedge insole for medial compartment disease (limited evidence).
• Intra articular corticosteroid injection for flares: triamcinolone acetonide 40 mg (or methylprednisolone acetate 40 to 80 mg) with lidocaine 1% 3 to 5 mL, for relief lasting 2 to 8 weeks. Limit to 3 to 4 per year per joint, avoid within 3 months before joint surgery, and monitor glucose in diabetes for 3 to 5 days. Hyaluronic acid injection (weekly for 3 to 5 weeks) has limited and inconsistent benefit.
• Surgery: arthroscopic partial meniscectomy is not advised for degenerative tears without mechanical locking, because it gives no benefit over exercise therapy and accelerates cartilage loss. Consider it only for persistent true mechanical locking or a displaced flap tear with failed conservative care of at least 3 months, and repair for selected tears in younger patients. Knee replacement (unicompartmental or total) for advanced osteoarthritis with failure of other treatment.
• Subchondral insufficiency fracture: protected weight bearing with crutches for 6 to 8 weeks, vitamin D and calcium review (cholecalciferol 1000 to 2000 IU daily), and orthopaedic referral.
• Special groups:
  • Elderly: favour exercise, topical agents and walking aids, and avoid NSAIDs in renal, cardiovascular and gastrointestinal disease.
  • Diabetes: monitor glucose after steroid injection.
  • Pregnancy: physiotherapy and paracetamol. Avoid NSAIDs after 20 weeks.
  • Renal impairment: avoid oral NSAIDs, and reduce tramadol dose.
  • Anticoagulation: aspiration and injection with a fine needle and pressure for 5 to 10 minutes.
• Follow up: review at 6 to 12 weeks. Refer to orthopaedics for true locking, instability, failed conservative care at 3 to 6 months, suspected subchondral fracture, or advanced osteoarthritis.