Review Question - QID 217469

This patient sustained a posterior knee dislocation. The most commonly associated injured structure is the peroneal nerve.

Knee dislocations are high-energy traumatic injuries characterized by a high rate of neurovascular injury. Diagnosis is made clinically with careful assessment of limb neurovascular status. Popliteal artery injuries occur approximately 16% of the time and have an amputation rate of up to 20%. Peroneal nerve injuries occur 25% of the time and have a 50% recovery rate; tibial nerve injury is less common than peroneal nerve injury. Radiographs should be obtained to document reduction. Treatment is generally emergent reduction and stabilization with an assessment of limb perfusion followed by delayed ligamentous reconstruction.

Boyce et al. reviewed acute knee dislocations. They reported that damage to the popliteal artery is a common associated injury that can be diagnosed on physical examination using ankle-brachial indices (ABIs), CT angiography, or standard angiography. They noted that after reduction, patients with a normal pulse examination and an ABI ≥0.9 may be observed, with serial examination performed to document vascular status and monitor for compartment syndrome, while patients with asymmetric pulses or an ABI <0.9 in the presence of pulses may be treated urgently depending on the results of additional vascular imaging. They concluded that patients with absent pulses and clear signs of vascular compromise should be treated emergently.

Halvorson et al. reviewed vascular injury following knee dislocation. They reported that vascular injury may be seen in up to 16% of patients with knee dislocation. They concluded that a thorough vascular assessment is essential and an arterial pressure index <0.90 is indicative of a potential vascular compromise.

Figure A is the lateral radiograph of the knee demonstrating a knee dislocation

Incorrect Answers:
Answers 1&2: The quadriceps and patellar tendons may be injured following a knee dislocation but are much less commonly involved compared to the peroneal nerve
Answer 4: Popliteal artery injuries occur approximately 16% of the time, whereas peroneal nerve injuries occur 25% of the time
Answer 5: The tibial nerve is less commonly injured compared to the peroneal nerve