A 29-year-old male, who was normally fit and well, presented to the emergency department following a fall playing football. The patient had stood on the ball, with the ball rolling under his weight and twisting his knee.
On examination, there was a prominence over the lateral aspect of the proximal left leg. He was exquisitely tender over the fibular head, with no obvious knee effusion. He was unable to weight bear but was neurovascularly intact, with no features of common peroneal nerve injury. His ankle joint was stable and non-tender, with no suggestion of disruption of the distal tibiofibular joint.
Plain radiographs of the knee were suggestive of proximal tibiofibular dislocation, with no overlap of the fibula and tibia on the anteroposterior (AP) film (Figure 1), and anterior displacement of the fibular head on the lateral film (Figure 2). Radiographs of the ankle confirmed no distal tibiofibular injury.
MRI of the knee was undertaken to confirm the diagnosis and exclude ligamentous injury; this confirmed anterolateral tibiofibular dislocation (Figures 3 and 4).
It also permitted us to further assess the common peroneal nerve, which can be injured in posterior fibular dislocation. The report notes:
The proximal fibula is dislocated anterolaterally from its usual position, with extensive high signal around the tibiofibular ligament.
There is diffuse high signal around the lateral collateral ligament with no significant disruption of the ligament itself.
Popliteus is intact. No injury to the common peroneal nerve is seen.
No fracture or tendon injury is demonstrated, and the remainder of the internal structures of the knee appear normal."
The patient was taken to the operation theatre for closed reduction under general anaesthesia, with the reduction visualized under the image intensifier (Figure 5), confirming a satisfactory outcome. The patient was discharged in an above-knee backslab for 2 weeks, non-weight bearing. Weight-bearing ability would be expected to improve significantly after this point.