Acute or degenerative tear of the medial or lateral meniscus causing joint-line pain, effusion, and mechanical symptoms.
Also known as: meniscus tear, meniscal tear, medial meniscus, lateral meniscus
Overview
Tear of the fibrocartilaginous meniscus of the knee. Acute tears typically result from a twisting injury on a planted foot in younger active patients. Degenerative tears occur in middle-aged and older adults often with minimal or no recalled trauma and coexisting OA.
Epidemiology
One of the most common knee injuries. Acute tears peak in athletes 20-40. Degenerative tears prevalent in adults >40, especially with knee OA.
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The menisci distribute load and stabilize the knee. A twisting force on the flexed and loaded knee — or repetitive degenerative wear — produces a tear. The peripheral 'red-red' zone (outer 1/3) is vascularized and may heal; the inner 'white-white' zone is avascular and does not heal. Tear morphology (radial, horizontal, longitudinal, complex, bucket-handle, root tear) influences treatment.
Clinical presentation
Symptoms
Acute tear: twisting injury, often with a popping sensation, followed by pain along the joint line
Effusion developing over 12-24 hours (slower than ACL effusion)
Mechanical symptoms: catching, locking, giving way
Degenerative tear: insidious medial joint-line pain, may follow squatting or rising from chair, often with coexisting OA symptoms
Signs / physical exam
Joint-line tenderness (medial > lateral) — best clinical sign
Effusion
Positive McMurray test (joint line pain or click with flexion and rotation)
Positive Thessaly test (pain with internal/external rotation while standing on the affected leg)
Positive Apley grind test (prone, knee flexed 90 degrees, axial compression plus tibial rotation reproduces joint-line pain); pain with deep squatting
Reduced flexion or true mechanical block to extension (consider bucket-handle tear)
Differential diagnosis
ACL tear — Audible pop, immediate large effusion, instability; positive Lachman; often coexists with meniscus tear (especially lateral)
Medial collateral ligament (MCL) sprain — Valgus mechanism; tenderness along medial joint line above and below; pain with valgus stress
Patellofemoral pain syndrome — Anterior knee pain with stairs, prolonged sitting; no joint-line tenderness or mechanical symptoms
Osteoarthritis — Insidious onset, X-ray findings, often coexists with degenerative meniscal tears
Osteochondral lesion — Catching/locking, X-ray or MRI changes
Pes anserine bursitis — Tender ~5 cm distal to the medial joint line at the pes anserine insertion
Loose body — Episodic locking, joint-line pain, MRI/CT diagnostic
Retear after repair (especially in white-white zone)
Locked knee with unrepaired bucket-handle tear
PANCE pearls
Joint-line tenderness is the single most useful exam finding for meniscal tear.
Knee that cannot fully extend after a twisting injury is concerning for a bucket-handle tear — urgent orthopedic referral.
Arthroscopic partial meniscectomy does not outperform physical therapy or sham for degenerative meniscus tears with OA (MeTeOR, ESCAPE trials) — counsel patients accordingly.
Meniscal repair is preferred over meniscectomy whenever the tear is in the vascular zone and the patient is young — preserves cartilage.
Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants.