In acute compartment syndrome of the leg, which compartment is most commonly involved?

• A. Anterior compartment of the leg
• B. Deep posterior compartment of the leg
• C. Dorsal compartment of the forearm
• D. Lateral compartment of the leg

Answer: (A)

Swelling inside a closed muscle compartment raises the pressure to levels that cut off blood flow and tissue perfusion. In the leg, the compartments are bound by relatively noncompliant fascia, so when injury causes edema or bleeding, pressure builds quickly.

The front (anterior) compartment is most commonly involved because it contains a large volume of muscle mass that tends to swell after trauma, and its fascia is particularly inelastic. The muscles here—the tibialis anterior and the extensor group—are highly active and prone to edema after injury, so pressure rises more readily than in other leg compartments. This combination of substantial muscle content and tight fascia makes ischemia more likely in the anterior compartment, leading to the classic pain out of proportion to exam and pain with passive stretch.

Other compartments can be affected, but less frequently. The dorsal forearm compartment mentioned in the distractor is outside the leg entirely, which is why it isn’t a correct target here. In suspected cases, rapid assessment and treatment are essential to prevent ischemic injury.