Meniscus Injuries
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Direct answer
A meniscus tear follows a twisting injury on a flexed, weight-bearing knee, presenting with joint line pain, effusion, catching or giving way, and — when a bucket-handle fragment flips across the joint — sudden inability to fully extend the locked knee. Joint line tenderness with a positive McMurray test suggests the diagnosis, MRI confirms it, and treatment ranges from physiotherapy for degenerate tears to arthroscopic repair or partial meniscectomy for mechanical tears, with repair preferred in the vascular peripheral third and in the young.
What you must remember
- Mechanism: rotational force on a flexed, loaded knee; the medial meniscus, being less mobile and firmly attached to the capsule, tears more often than the lateral.
- Symptoms and signs: joint line tenderness is the most useful bedside sign, with effusion, clicking, catching and giving way; the McMurray test — flexion-rotation-extension with a click or pain — supports the diagnosis.
- Tear shapes: bucket-handle (longitudinal with a displaced fragment), radial, parrot-beak, horizontal cleavage in older patients and complex degenerate tears.
- The locked knee: a bucket-handle tear jammed in the intercondylar notch blocks full extension — a mechanical block needing arthroscopic treatment, not simply physiotherapy.
- Red versus white zone: the outer third is vascularised (red zone) and heals after repair; the inner two-thirds (white zone) is avascular, so irreparable tears undergo minimal partial meniscectomy — preserving as much meniscus as possible to delay osteoarthritis.
- Degenerate tears in middle-aged and older knees — with or without early osteoarthritis — are managed first with structured physiotherapy, since arthroscopy offers no added benefit in the absence of mechanical locking.
- Discoid meniscus, almost always lateral and congenital, presents in children and adolescents with snapping and early tears, often needing arthroscopic saucerisation or repair.
Common confusion
Locked knee has two meanings and the exam exploits both: a true mechanical block from a displaced bucket-handle tear, and the pseudolocking of a painful, guarded knee after patellar dislocation — only the meniscal block meets a firm endpoint. Students then blur traumatic tears in the young with degenerate tears in the older: the first is repaired where possible, the second is exercised first, with arthroscopy reserved for genuine mechanical symptoms. Remember that the medial meniscus, anchored to the deep MCL, travels with MCL injuries.
Exam-focused takeaway
NEET-PG stems describe a twisting injury on a loaded knee with later joint line tenderness and ask for the test (McMurray) and the confirmation (MRI). The locked knee vignette is a favourite: sudden loss of extension after a twist means a bucket-handle tear needing arthroscopy. Classification one-liners test the red versus white zone as the decision between repair and partial meniscectomy, and the medial meniscus as the commoner tear because it is less mobile. Degenerate-tear stems test conservative management with physiotherapy first, and paediatric stems pair a snapping knee with a discoid lateral meniscus. Expect accompanying ACL injury to be built into unstable-knee vignettes.
Frequently asked questions
How does a meniscal tear classically occur?
By a twisting force on a flexed, weight-bearing knee, producing joint line pain, effusion, catching and later giving way.
What is the McMurray test?
Flexion and rotation of the knee followed by extension, with a palpable or painful click over the joint line suggesting a meniscal tear.
What is a locked knee?
Sudden inability to fully extend the knee, most often from a bucket-handle meniscal fragment displaced into the intercondylar notch, requiring arthroscopic treatment.
Which meniscal tears are repaired?
Tears in the vascular peripheral red zone, especially longitudinal ones in young patients; avascular white-zone tears undergo minimal partial meniscectomy.
What is a discoid meniscus?
A congenitally thick, disc-shaped lateral meniscus that snaps in childhood and adolescence and tears early, often treated by arthroscopic saucerisation.