Tibia-fibular Joint Dislocation.

A 17-year-old man presented with acute left lateral knee pain after “twisting” his knee during a soccer scrimmage. He denied trauma and prior injury to that knee. He was unable to bear weight but denied neurovascular symptoms. Examination revealed a prominence deformity and significant tenderness over the lateral knee distal to the joint line, in the region of the fibular head. During his emergency department (ED) evaluation, he had intact peroneal nerve function. A picture of his legs is shown in Figure 1.

Figure 1.

Picture of patient presenting with knee pain and deformity of left lateral knee

Proximal tibiofibular joint (PTFJ) dislocation is an unusual injury, occurring in less than 1% of knee injuries. It has been reported in soccer, rugby, and football players, ballet dancers, parachutists and snowboarders.1,2 It typically occurs when the knee is slightly flexed and the foot is rotated and plantar flexed.2 Radiographic findings can be subtle, and diagnosis is fostered when comparison films are obtained. When in doubt, computed tomography should be obtained.3 Our radiographs demonstrated widening of the PTFJ of the left knee; comparison to the right (uninjured) knee confirms the diagnosis (Figure 2).

Figure 2.

Anterior-posterior radiograph showing widening of the left proximal tibiofibular joint

We were unable to reduce the dislocation despite moderate sedation with etomidate. The patient was also seen by orthopedic surgery in the ED. At follow-up two days later, he was noted to have mildly decreased sensation in the peroneal nerve distribution. He was scheduled for surgery, but prior to repair he slipped and felt a “pop.” Pre-operative radiographs revealed that the dislocation had spontaneously reduced.