A case report of orbital blow-out fracture with medial rectus muscle entrapment is described. Over one-third of the patients with blow-out fractures of the orbital floor also sustain medial wall injury. Five previous case reports of medial entrapment are reviewed. The mechanism of injury is hydraulic, and the medial muscle incarceration in the fracture may produce an orbital retraction syndrome. Exploratory surgery is recommended through an external orbito-ethmoid approach.