Knee trauma
Acute knee trauma spans ligament sprains, meniscal tears, extensor-mechanism injury, and fracture-dislocation, with the anterior cruciate ligament injured most often; the first priority is excluding knee dislocation with popliteal artery injury and compartment syndrome before treating the specific ligamentous or meniscal pattern.
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What this article covers
- Overview
Acute injury to the knee's stabilizing and load-bearing structures: knee trauma covers ligamentous (ACL, PCL, MCL, LCL), meniscal, extensor-mechanism, and osseous (tibial plateau, patella) injuries…
- Epidemiology
Injuries cluster in "stop-and-go" pivoting sports (soccer, basketball, gymnastics), where sudden deceleration and directional change load the ACL.
- Risk factors
Sudden cutting, pivoting, or deceleration in a pivoting sport is the strongest risk factor for ACL tear.
- Pathophysiology
The ACL's anteromedial and posterolateral bundles resist anterior tibial translation relative to the femur; disruption produces the "giving way" instability patients feel while pivoting.
- Clinical features
A "pop" followed by rapid, bloody hemarthrosis within hours is the hallmark of an ACL tear; patients report instability or the knee "giving out" while pivoting.
- Differential diagnosis
Tibial plateau fracture: a fracture line is visible on plain radiograph, unlike normal bony architecture in a pure ligament/meniscal injury.
- Diagnosis
Diagnosis is established clinically by mechanism plus a structure-specific stress test, then confirmed by imaging: a positive Lachman test (anterior tibial translation without a firm endpoint)…
- Management
First, treat any high-energy mechanism, gross deformity, or diminished distal pulses as a knee dislocation until proven otherwise: reduce the joint immediately, splint in slight flexion, and obtain…
- Complications
Popliteal artery injury with limb ischemia is the most immediately limb-threatening complication of knee dislocation and requires emergent revascularization.
- Prognosis
An untreated ACL tear does not heal, so instability and secondary cartilage or meniscal damage persist without reconstruction or a committed bracing and strengthening program.
- Prevention
Obtain an ankle-brachial index or Doppler study in every suspected or confirmed knee dislocation, regardless of a normal pulse exam, since intimal popliteal injury can be clinically silent.
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