Meniscal Injury

In traumatic tears, the history is a specific twisting mechanism on a loaded flexed knee, followed by joint-line pain and an effusion that develops over hours. An immediate tense haemarthrosis within minutes strongly suggests ACL rupture, osteochondral injury, or fracture, not isolated meniscal injury. Mechanical symptoms - catching, clicking, locking, giving way - are common. True locking, a fixed flexion deformity from a displaced fragment that cannot be passively extended, must be distinguished from pseudo-locking caused by pain or guarding.

Degenerative tears affect patients over 40 with no clear traumatic mechanism. Medial knee pain, morning stiffness, and intermittent swelling are typical and may be clinically indistinguishable from medial-compartment OA.

Examination: joint-line tenderness is the most sensitive clinical sign (70-90% sensitivity); palpate medial and lateral joint lines at 90 degrees of flexion. The McMurray test (palpable click with joint-line pain on knee flexion-rotation-extension) has good specificity but moderate sensitivity - a negative McMurray does not exclude a tear. Thessaly (joint-line pain on standing at 20 degrees of flexion with rotation) is a useful adjunct. Always assess the ACL with the Lachman test - ACL and meniscal injuries commonly coexist. Palpate for meniscal cysts at the joint line, especially laterally.

Key differentials: ACL rupture (immediate haemarthrosis, positive Lachman), MCL sprain (valgus stress positive at 30 degrees), knee OA, patellofemoral pain, pes anserine pain syndrome, Baker cyst, ITBS (lateral epicondylar tenderness rather than joint-line), and tibial plateau fracture after significant trauma.

MRI is most useful when the result will change management. Plain weight-bearing radiographs (AP, lateral, with or without skyline) do not show the menisci directly but exclude fracture, assess for osteoarthritis, evaluate alignment, and identify loose bodies. Weight-bearing views are essential for accurate OA assessment.

MRI is the investigation of choice when a suspected tear will change management - a locked knee, clear acute injury with mechanical symptoms, suspected repairable tear, associated ACL injury, or genuine diagnostic uncertainty. Per NICE NG226, MRI is not routinely indicated for likely degenerative tears in older adults with knee OA. The critical caveat is that MRI shows tears in up to 60% of asymptomatic adults over 50, so the scan must always be interpreted alongside the clinical picture.

Ultrasound has a limited role for meniscal assessment but may demonstrate effusion, Baker cyst, or meniscal cyst. Aspirate a tense acute haemarthrosis if needed; fat droplets (lipohaemarthrosis) indicate intra-articular fracture.

The fundamental principle is the traumatic vs degenerative distinction.

Degenerative tears in the context of knee OA are managed conservatively per NICE NG226: therapeutic exercise (quadriceps strengthening is the priority, supported by the ESCAPE trial), weight management, and topical then oral NSAIDs. Arthroscopic partial meniscectomy is NOT recommended per NICE NG226 and the UK Evidence-Based Interventions list - multiple RCTs (ESCAPE, FIDELITY) show no benefit over structured exercise at 12-24 months. A minimum of 3-6 months of structured rehabilitation precedes any surgical consideration. The exception is true mechanical locking preventing rehabilitation.

Traumatic tears in younger patients: protect the knee initially with PEACE & LOVE principles, early range-of-motion work as pain allows, and quadriceps activation. Many traumatic tears are managed non-operatively in the first instance. MRI and orthopaedic referral are indicated for clear acute injury with mechanical symptoms, a locked knee, a suspected repairable tear, or an associated ACL injury.

Where surgery is offered, the choice between repair and meniscectomy depends on tear pattern (vertical longitudinal in the peripheral zone favours repair), location (vascular zone), and patient factors (younger, active). Concurrent ACL reconstruction improves repair outcomes. The mantra is repair whenever possible, resect as little as necessary - meniscectomy accelerates osteoarthritis, particularly in an ACL-deficient knee where the medial meniscus becomes the primary restraint to anterior tibial translation.

A locked knee from a bucket-handle tear requires urgent MRI and orthopaedic referral - prolonged displacement risks further chondral damage.

Conservative management (degenerative tears or non-operative traumatic tears): per NICE NG226, treat as knee osteoarthritis. Quadriceps strengthening is the priority, with hamstring and hip strengthening, range-of-motion work, aerobic fitness, and weight management as core components. For non-operative traumatic tears, early range-of-motion is essential - full extension is the priority - alongside quadriceps activation and progressive strengthening before a graduated return to activity.

Post-arthroscopic partial meniscectomy: recovery is relatively rapid. Weight-bearing as tolerated immediately, early range-of-motion with full extension as the priority, and quadriceps activation from day one. Return to sport is typically 4-8 weeks, criteria-based.

Post-meniscal repair: recovery is slower because the repair must heal. Protocols vary by surgeon and tear pattern, but broad principles are 0-2 weeks in a brace in extension with partial weight-bearing, 2-6 weeks progressive range-of-motion and weight-bearing, 6-12 weeks full weight-bearing with progressive strengthening, jogging from around 12-16 weeks when cleared, and return to sport typically 4-6 months.

Ongoing quadriceps and lower-limb strengthening with weight management is essential indefinitely after meniscectomy, because loss of meniscal tissue increases long-term osteoarthritis risk.

• •NICE NG226 (2022) - Osteoarthritis assessment and management: structured exercise is first-line for degenerative meniscal tears in the context of OA; arthroscopic partial meniscectomy is not recommended.
• •ESCAPE trial (van de Graaf, 2018, JAMA) - Exercise therapy was non-inferior to arthroscopic partial meniscectomy at 24 months for degenerative tears.
• •FIDELITY trial (Sihvonen, 2013, NEJM) - No benefit of partial meniscectomy over sham surgery for degenerative tears with mechanical symptoms.
• •UK Evidence-Based Interventions guidance - Arthroscopic knee surgery for OA is on the do-not-perform list outside specific clinical exceptions.
• •BASK / BESS pathway principles - Meniscal preservation is preferred in younger patients; meniscectomy accelerates OA, particularly in ACL-deficient knees.

• •The most testable distinction is traumatic vs degenerative; degenerative tears in OA are managed conservatively per NICE NG226 (ESCAPE, FIDELITY) and meniscectomy is on the UK EBI do-not-perform list.
• •True locking (a fixed flexion deformity that cannot be passively extended) is a displaced bucket-handle fragment - an urgent orthopaedic problem. Pseudo-locking from pain or guarding is not the same thing.
• •Meniscal vascularity determines healing: red-red zone repairs, white-white zone does not - one of the most commonly tested concepts.
• •Repair whenever possible, resect as little as necessary; meniscectomy accelerates OA, especially in an ACL-deficient knee where the medial meniscus is the secondary restraint to anterior tibial translation.
• •An immediate tense haemarthrosis within minutes suggests ACL rupture, osteochondral injury, or fracture - not isolated meniscal injury (which produces effusion over hours).
• •MRI shows tears in up to 60% of asymptomatic adults over 50 - treat the patient, not the scan.