Meniscal Tears — Types & Repair

Meniscal tears are the most common knee injury requiring surgical intervention. The medial and lateral menisci are fibrocartilaginous C-shaped structures that serve critical functions — load transmission (they transmit approximately 50% of the compressive load in extension and 85% in flexion), shock absorption, joint stability, lubrication, and proprioception. Understanding the tear pattern, its location relative to the vascular supply, and the principles of repair versus resection is fundamental to knee surgery practice.

• The medial meniscus is less mobile (attached to the medial capsule and MCL), crescent-shaped, and more commonly torn; the lateral meniscus is more mobile, O-shaped (near-circular), covers more of the tibial plateau, and has a popliteus hiatus posterolaterally
• Vascular zones of the meniscus: the meniscus is divided into three zones based on vascularity — the red-red zone (peripheral 25–30% of the meniscal width — well-vascularised from the perimeniscal capillary plexus; highest healing potential; ideal for repair); the red-white zone (the middle transitional zone — partial vascularity; marginal healing potential); the white-white zone (the inner 25–30% — avascular; no healing potential; tears in this zone should be resected); the location of a tear relative to these zones is the primary determinant of whether repair is appropriate
• The meniscus receives its vascular supply from the perimeniscal capillary plexus arising from the medial and lateral geniculate arteries; the inner two-thirds of the meniscus receives nutrients by diffusion from synovial fluid; the outer one-third is supplied directly by the capillary plexus

• History: acute trauma (young patient — twisting injury often with ACL); insidious onset (degenerative — middle-aged patient, no clear injury); mechanical symptoms (clicking, catching, giving way, locking); joint line pain; effusion; locking (inability to fully extend the knee = bucket-handle tear until proven otherwise)
• McMurray test: the most widely used clinical test for meniscal tears; patient supine; hip and knee fully flexed; for medial meniscus — apply valgus stress + external tibial rotation; slowly extend the knee; a palpable `clunk` at the medial joint line = positive medial McMurray; for lateral meniscus — apply varus stress + internal tibial rotation; a clunk at the lateral joint line = positive lateral McMurray; sensitivity approximately 55–60%, specificity approximately 80–85%; the clunk (not just pain) is the positive finding — pain alone on McMurray is not specific
• Thessaly test: performed standing; the patient stands on one leg on the affected side with the knee in 20° flexion; the examiner holds the patient`s hands; the patient rotates the body medially and laterally three times; positive if joint line pain or locking sensation is reproduced; sensitivity approximately 89% (higher than McMurray), specificity approximately 97%; considered the most accurate single clinical test for meniscal tears
• Apley test (grinding test): prone position; knee flexed to 90°; downward compression force applied through the foot while internally and externally rotating the tibia; positive if joint line pain reproduced; the Apley distraction test (traction rather than compression) should be negative if the pain is meniscal — distinguishes meniscal from ligamentous pain
• Joint line tenderness: palpation of the joint line with the knee in slight flexion; medial or lateral joint line tenderness is the most sensitive (but not specific) sign for a meniscal tear on the respective side

• Plain radiographs: AP (weight-bearing), lateral, and 45° PA (tunnel view); assess for OA changes, joint space narrowing, loose bodies; X-rays are essential to exclude bony pathology and assess the degree of underlying OA (a key factor in management decisions)
• MRI: the investigation of choice for meniscal pathology; sensitivity approximately 90–95%, specificity 85–95% for medial meniscal tears; slightly lower sensitivity for lateral tears (due to the popliteus hiatus); MRI grades meniscal signal changes: Grade 1 — intrasubstance signal not reaching the articular surface; Grade 2 — linear intrasubstance signal not reaching the articular surface (early degeneration); Grade 3 — signal reaching the articular surface = tear; MRI also identifies associated ligamentous injuries, chondral damage, and bone bruising

• Non-operative management for degenerative tears: the evidence from multiple RCTs (FIDELITY 2013, METEOR 2013, ESCAPE 2017) demonstrates that APM is no better than physiotherapy or sham surgery for degenerative meniscal tears in patients with or without mild OA; NICE guidelines (2014, updated 2020) do not recommend APM for degenerative meniscal tears; non-operative management (physiotherapy, analgesia, activity modification) should be first-line; surgery may be considered in the rare patient who fails >3 months of structured non-operative management AND has clear mechanical symptoms (locking) attributable to a structural tear on MRI
• Indications for surgical treatment: true locked knee (bucket-handle tear causing extension deficit); acute traumatic tear in a young patient with mechanical symptoms failing non-operative treatment; peripheral tear in the red-red zone amenable to repair; associated ACL reconstruction (concurrent meniscal repair); complex tear with mechanical symptoms in a young patient
• Criteria for meniscal repair: peripheral tear in the red-red zone (or red-white zone in a young patient); tear length >1 cm; tear reducible and stable after probe testing (fragment reduces back to its bed); vertical longitudinal or bucket-handle pattern (most amenable to repair); young patient (<40 years preferably <35 years); tear associated with ACL reconstruction (the revascularisation from ACL reconstruction drilling improves the healing environment for meniscal repair); absence of significant OA
• Meniscal repair techniques: inside-out (sutures placed from inside the joint through the capsule — most reliable but requires accessory incision to retrieve suture ends); outside-in (sutures placed from outside in — for anterior horn tears); all-inside (all-suture devices placed arthroscopically — most commonly used; Fast-Fix, OmniSpan); the choice of technique depends on tear location
• Arthroscopic partial meniscectomy (APM): resection of the unstable inner fragment back to a stable rim; for tears not amenable to repair (avascular zone, horizontal cleavage, degenerative); the goal is to remove as little meniscus as possible while achieving a stable rim; `total` meniscectomy is never performed — it leads to rapid OA

• Total meniscectomy and OA: removal of the entire meniscus eliminates its load-sharing function; tibiofemoral contact stress increases dramatically after total meniscectomy; long-term studies show that total meniscectomy leads to radiological OA changes in virtually all patients within 10–20 years and clinical OA in the majority; even partial meniscectomy increases OA risk proportional to the volume of tissue removed; every attempt should be made to preserve meniscal tissue — repair is always preferable to resection in an appropriately selected candidate
• Meniscal repair with ACL reconstruction: concurrent meniscal repair at the time of ACL reconstruction has significantly improved healing rates compared to repair in an ACL-deficient knee; the perioperative inflammatory environment and vascular response from ACL graft tunnel drilling creates fibrin clots and growth factors that improve the meniscal repair healing milieu; healing rates of 85–90% are reported for peripheral meniscal repairs performed at the time of ACLR vs 60–70% for isolated meniscal repair
• Meniscal allograft transplantation (MAT): for young patients with prior subtotal or total meniscectomy who develop symptomatic medial or lateral compartment OA or pain from meniscal deficiency; a fresh-frozen size-matched meniscal allograft is transplanted arthroscopically or through a mini-arthrotomy; requires intact articular cartilage (no advanced OA) and correct limb alignment; MAT can delay or reduce the need for arthroplasty in young patients; evidence for long-term benefit is improving; technically demanding procedure limited to specialist knee centres

• Vascular zones: red-red (outer 25–30% — vascularised, heals = repair); red-white (transitional — marginal healing); white-white (inner — avascular, no healing = resect)
• Bucket-handle tear: vertical longitudinal; displaced fragment in notch; locked knee (extension deficit); young patient with ACL injury; always attempt repair if peripheral
• McMurray test: valgus + ER for medial; varus + IR for lateral; positive = palpable CLUNK at joint line (not just pain); sensitivity ~55–60%, specificity ~80–85%
• Thessaly test: single-leg stance at 20° flexion; body rotation; positive if joint line pain reproduced; most sensitive single test (sensitivity ~89%, specificity ~97%)
• Degenerative meniscal tears: FIDELITY + METEOR + ESCAPE trials — APM no better than physiotherapy or sham surgery; NICE does not recommend APM for degenerative tears; first-line = non-operative management
• Repair criteria: peripheral red-red zone; >1 cm; young patient (<35–40 years); reducible; vertical/bucket-handle; ± concurrent ACL reconstruction (improves healing to 85–90%)
• Radial tear: disrupts circumferential fibres; complete radial tear = equivalent to total meniscectomy biomechanically; repair if possible; flap tears of inner free edge — resect
• Total meniscectomy: NEVER indicated; leads to OA in virtually all patients at 10–20 years; even partial meniscectomy increases OA proportional to volume removed
• Horizontal cleavage tear: associated with parameniscal cysts (lateral > medial); drain cyst through tear during arthroscopy; resect unstable leaf
• MAT: for young patients with prior meniscectomy + early OA; intact cartilage + correct alignment required; delays arthroplasty; specialist centres only