Musculoskeletal · Knee Pathology
The facts most likely to be tested
Patients with a meniscus tear classically present with joint line tenderness, locking, catching, or giving way of the knee.
The McMurray test is the most common physical exam maneuver used to elicit a painful click or pop during knee flexion and rotation.
The Thessaly test is a highly sensitive and specific weight-bearing maneuver performed by rotating the knee while the patient stands on one leg.
MRI of the knee is the gold standard diagnostic imaging modality to confirm the presence and location of a meniscal tear.
The medial meniscus is injured significantly more frequently than the lateral meniscus due to its firm attachment to the medial collateral ligament (MCL).
Initial management for stable, degenerative, or small peripheral tears is conservative therapy consisting of physical therapy, activity modification, and NSAIDs.
Arthroscopic partial meniscectomy or meniscal repair is indicated for patients with persistent mechanical symptoms or failure of conservative management.
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A 28-year-old male presents to the clinic complaining of persistent right knee pain following a twisting injury while playing soccer three weeks ago. He reports that his knee occasionally feels like it is locking in place, requiring him to manually manipulate it to regain full range of motion. On physical examination, there is localized joint line tenderness along the medial aspect of the knee. A McMurray test produces a palpable click accompanied by sharp pain. The knee is stable to varus and valgus stress testing.
What is the most appropriate next step in the management of this patient?
MRI of the knee
The patient's history of mechanical symptoms (locking) and positive McMurray test are highly suggestive of a meniscal tear, necessitating MRI to confirm the diagnosis and guide surgical planning.
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High yield triage
Etiology / Epidemiology
Common in young athletes via twisting injury or older adults via degenerative wear. Medial meniscus is more commonly injured than lateral.
Clinical Manifestations
Presents with joint line tenderness, locking, or catching of the knee. McMurray test is the classic physical exam maneuver.
Diagnosis
The MRI is the gold standard for definitive diagnosis. Clinical diagnosis is often sufficient for initial management.
Treatment
Initial management is conservative (RICE, NSAIDs, PT). Surgical meniscectomy or repair is reserved for persistent symptoms.
Prognosis
High success rate with PT; however, untreated tears increase risk of early-onset osteoarthritis.
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Epidemiology & Etiology
Acute tears typically occur in younger patients during sports involving sudden pivoting or deceleration. Degenerative tears are common in older adults due to cumulative microtrauma. The medial meniscus is more frequently injured due to its firm attachment to the medial collateral ligament.
Pertinent Anatomy
The meniscus consists of fibrocartilage providing shock absorption and load distribution. The peripheral 1/3 is vascularized (the red zone), allowing for potential healing, while the inner 2/3 is avascular (the white zone).
Pathophysiology
Tears result from shear forces during knee rotation while the joint is flexed. Degenerative tears occur as collagen fibers weaken with age, leading to horizontal or complex cleavage patterns. Mechanical symptoms arise when a displaced fragment causes locking or catching within the joint space.
Clinical Manifestations
Patients report a popping sensation followed by joint line tenderness and effusion. Classic findings include locking (inability to fully extend) and catching. Red flags include significant hemarthrosis or inability to bear weight, which may suggest an associated ACL tear.
Diagnosis
Physical exam includes the McMurray test and Apley grind test. While clinical diagnosis is often accurate, MRI is the gold standard for confirming tear location and morphology. Radiographs are primarily used to rule out fractures or advanced osteoarthritis.
Treatment
Initial treatment is conservative therapy including rest, ice, and NSAIDs. Physical therapy focuses on quadriceps strengthening to stabilize the joint. Surgical meniscectomy or meniscal repair is indicated for patients with persistent mechanical symptoms or failure of conservative management. Avoid aggressive weight-bearing immediately post-repair.
Prognosis
Most patients return to baseline function with physical therapy. Long-term complications include early-onset osteoarthritis due to altered joint mechanics. Monitoring for persistent pain or instability is required.
Differential Diagnosis
ACL tear: associated with a 'pop' and immediate hemarthrosis
MCL injury: pain localized to the medial joint line with valgus stress
Patellofemoral syndrome: anterior knee pain exacerbated by stairs
Osteoarthritis: chronic pain with morning stiffness and joint space narrowing
Loose body: intermittent locking without history of acute trauma