Meniscal Tears — Basics

Meniscal tears are among the most common knee injuries encountered in orthopaedic practice. The menisci are crescent-shaped fibrocartilaginous structures that serve critical biomechanical functions. Their preservation is paramount — loss of meniscal tissue leads to accelerated cartilage degeneration and premature knee osteoarthritis.

• Functions of the meniscus: load transmission (transmits 50–70% of compressive knee load in extension; up to 85% in flexion), shock absorption, joint stability (particularly in ACL-deficient knee), joint lubrication, and proprioception
• Total meniscectomy increases peak contact stress by 235–700% — the case for meniscal preservation is biomechanically overwhelming
• Medial meniscus: C-shaped; more firmly attached peripherally — less mobile; higher tear rate; posterior horn most commonly torn
• Lateral meniscus: more circular (O-shaped); more mobile; popliteus hiatus posterolaterally reduces peripheral attachment; lower tear rate but more discoid variants
• Vascular supply: peripheral 10–30% (red zone) — vascularised from capsular vessels; central 70–90% (white zone) — avascular; tears in the red zone heal; tears in the white zone do not
• Red-red zone (entirely peripheral): best healing potential; red-white zone (at vascular margin): intermediate healing; white-white zone (entirely avascular): poor healing — debridement preferred

Tear pattern, location, stability, and chronicity all influence management decisions. Understanding tear morphology is essential for surgical planning.

• History: acute (twisting injury, often with ACL) vs chronic/degenerative (no clear mechanism, >40 years); joint line pain; swelling (delayed — hours after injury distinguishes from ACL haemarthrosis); mechanical symptoms (locking, catching, clicking, giving way)
• True locked knee (inability to fully extend) = bucket-handle tear until proven otherwise — urgent arthroscopic assessment and reduction/fixation
• Joint line tenderness: most sensitive clinical sign — medial or lateral; specificity improves when combined with other tests
• McMurray test: valgus stress + external rotation (medial meniscus); varus stress + internal rotation (lateral meniscus); painful click in flexion-extension arc = positive; sensitivity 53%, specificity 59–97%
• Thessaly test (standing): weight-bearing twisting at 20° flexion — sensitivity 66–89%; more sensitive than McMurray for degenerative tears
• Apley grind test: prone, knee at 90° — compression and rotation; distraction relieves pain; distinguishes meniscal from ligamentous injury
• Assess for associated ACL laxity (Lachman, anterior drawer), MCL/LCL, and articular cartilage pathology (crepitus, effusion, bone-on-bone symptoms)

• Plain radiographs (weight-bearing AP, lateral, Rosenberg view): exclude bony injury; assess joint space narrowing, alignment, and articular changes; Rosenberg view (45° flexion weight-bearing PA) most sensitive for medial compartment joint space narrowing — better predictor of cartilage loss than standard standing AP
• MRI: investigation of choice — sensitivity 85–95%, specificity 85–90% for meniscal tears; assess tear pattern, location, displacement, and articular cartilage; grade signal intensity (Grade 3 = tear communicating with articular surface); evaluate root attachments
• MRI grading: Grade 1 = intrameniscal signal (degeneration); Grade 2 = linear signal not reaching surface; Grade 3 = signal reaching articular surface = tear
• MR arthrogram: improves sensitivity for post-operative meniscus and subtle tears; not routine for primary diagnosis
• Diagnostic arthroscopy: gold standard; indicated when MRI inconclusive and clinical suspicion high; allows simultaneous treatment

• Non-operative management appropriate for: stable peripheral tears (<1 cm longitudinal tears in red zone), asymptomatic degenerative tears in older patients, and tears without mechanical symptoms or significant functional limitation
• NICE and ESSKA guidelines: degenerative meniscal tears in middle-aged patients without mechanical symptoms should be managed non-operatively first — physiotherapy-directed quadriceps strengthening, weight management, activity modification
• The METEOR and ESCAPE trials demonstrated that arthroscopic partial meniscectomy for degenerative meniscal tears offers no significant benefit over supervised physiotherapy at 2 years — non-operative management is first-line for degenerative tears
• Corticosteroid injection: for pain management in degenerative tears with associated OA; temporary relief; not disease-modifying
• PRP injection: emerging evidence; not yet standard of care for meniscal pathology
• Follow-up: reassess at 3 months; consider surgical intervention if symptoms persist despite adequate conservative management

The overriding surgical principle is meniscal preservation — repair is always preferred over resection when feasible.

Indications for Repair:

• Vertical longitudinal tear >1 cm in red or red-white zone
• Bucket-handle tear — urgent repair or reduction; if irreparable, partial meniscectomy of bucket-handle fragment
• Tear in young patient (<40 years) with repairable tissue quality
• Posterior root tears — transtibial pull-through suture repair
• Concurrent ACL reconstruction — simultaneous ACL reconstruction improves meniscal repair healing rate due to synovial stimulation; ideal biological environment for repair

Repair Techniques:

• Partial meniscectomy: for irreparable tears — remove minimum amount of unstable tissue; preserve as much functional rim as possible; aim to leave a stable, contoured rim; avoid levelling or smoothing of stable tissue
• Posterior root repair: transtibial pull-through with 2–3 sutures looped around posterior root; tied over anterior tibial cortical button; biomechanically restores hoop stress function
• Meniscal transplantation: for young patients with prior subtotal or total meniscectomy and symptomatic compartment; size-matched allograft; good intermediate-term results — delays but does not prevent OA progression

• Posterior root tears are the most underdiagnosed significant meniscal injury — medial posterior root tear causes meniscal extrusion, hoop stress failure, and rapid medial compartment OA; look for ghost sign on coronal MRI (absent posterior horn in coronal view due to extrusion)
• Radial tears disrupt circumferential fibres: biomechanically equivalent to total meniscectomy when complete; urgent repair consideration in young patients regardless of zone; use all-inside or inside-out horizontal mattress sutures
• Meniscal repair with ACL reconstruction: simultaneous repair in the context of ACL reconstruction improves healing rate from approximately 50% to 80% — the synovial fluid and fibrin clot stimulation from ACL tunnel preparation creates an ideal biological environment; always repair repairable meniscal tears at time of ACL reconstruction
• Failure of conservative management for degenerative tears: if mechanical symptoms (true locking, catching) persist despite 3 months of physiotherapy, partial meniscectomy is appropriate — MRI to distinguish true mechanical tear from degenerative signal change is critical; avoid operating on Grade 1–2 MRI signal in asymptomatic patients
• Post-repair rehabilitation: protected weight bearing for 4–6 weeks after repair; avoid deep flexion beyond 90° for 6 weeks; full return to sport at 4–6 months; accelerated protocols may be appropriate with stable repairs in concurrent ACL reconstruction

• Meniscus transmits 50–70% compressive load; total meniscectomy increases contact stress by up to 700%
• Red zone (peripheral 10–30%) = vascular = heals; white zone = avascular = does not heal
• Bucket-handle tear = locked knee = urgent arthroscopic treatment
• Radial tear = disrupts circumferential fibres = functionally equivalent to total meniscectomy — repair if possible
• Posterior root tear = meniscal extrusion = hoop stress failure = rapid OA; look for ghost sign on MRI
• METEOR and ESCAPE trials: partial meniscectomy for degenerative tears = no benefit over physiotherapy — non-operative first
• ACL reconstruction + simultaneous meniscal repair = improved healing rate (50% → 80%)
• Inside-out repair: gold standard posterior horn; protect saphenous nerve (medial) and peroneal nerve (lateral)
• Rosenberg view (45° flexion WB PA): most sensitive for medial compartment cartilage loss
• Meniscal transplantation: young patient, prior meniscectomy, symptomatic — delays but does not prevent OA