Figure A shows a proximal tibiofibular dislocation with comparison radiographs of the contralateral knee shown in Illustration A. Figures B and C do not indicate any cruciate ligament, meniscus, or osteochondral damage. Anterior tarsal tunnel syndrome secondary to deep peroneal nerve entrapment can be evaluated by EMG, but this patient's peroneal nerve symptoms are secondary to the proximal tibiofibular dislocation and instability.
The review article by Sekiya and Kuhn note that there are 4 types of dislocation with anterolateral being the most common and the diagnosis is most likely missed at high rate. Injury to the proximal tibiofibular joint is typically seen in athletes who sustain twisting motions of the flexed knee. They also note that the history and findings are often similar to lateral meniscus injuries.
Parkes and Zelko performed a case study of an isolated proximal tibiofibular joint after minor trauma. With acute injury, patients usually complain of pain and a prominence in the lateral aspect of the knee. Closed reduction is done by placing an appropriately directed force to the fibular head with the knee flexed between 80° and 110°, which relaxes the lateral collateral ligament and biceps femoris tendon. It is controversial as to whether immobilization for a few weeks or immediate range of motion is the preferred postreduction prescription. Open reduction is indicated for the acute dislocation that is not able to have a successful closed reduction. For patients with malreductions, missed dislocation, chronic pain or continued instability, surgical options include arthrodesis, fibular head resection, and proximal tibiofibular joint capsule reconstruction.
Parkes JC 2nd, Zelko RR. Isolated acute dislocation of the proximal tibiofibular joint. Case report. J Bone Joint Surg Am. 1973 Jan;55(1):177-83.
PMID:4691655 (Link to Abstract)
Sekiya JK, Kuhn JE. Instability of the proximal tibiofibular joint. J Am Acad Orthop Surg. 2003 Mar-Apr;11(2):120-8.
PMID:12670138 (Link to Abstract)