Background: Patients who are comatose after a traumatic brain injury often have heterotopic periarticular ossification that can be treated with excision to improve the range of motion of the joint.Methods: Areas of periarticular ossification were resected at an average of twenty-three months after recovery from a coma in seven knees of five patients who had a traumatic brain injury. Before the procedure, all of the knees were fixed in a flexed position that ranged from 10 to 40 degrees and they had a painful arc of motion that ranged from 20 to 70 degrees of flexion. None of the patients could walk, and some of them could barely sit in a wheelchair. At the end of the operation, the arc of motion was markedly improved in all of the knees (0 to 130 degrees in three knees, 0 to 120 degrees in three, and 10 to 120 degrees in one). In an attempt to prevent postoperative loss of motion and recurrence of the ossification, continuous passive motion was applied to the involved knee for six weeks before a full rehabilitation program was started. The latest follow-up evaluation was at an average of thirty-four months (range, twenty-five to sixty months).Results: At the time of follow-up, all of the patients could walk and all of the knees were pain-free. One knee had an arc of flexion of 0 to 90 degrees; two, an arc of 10 to 100 degrees; one, an arc of 5 to 110 degrees; two, an arc of 0 to 120 degrees; and one, an arc of 0 to 130 degrees. Ossification did not recur in any of the knees.Conclusions: Patients with good neuromuscular control had the best general functional result. The routine use of a continuous-passive-motion machine was associated with no recurrence of ossification, and there was some late loss of motion after its use was discontinued.