Proximal tibiofibular joint dislocation

Proximal tibiofibular joint dislocations (PTJD) are a form of proximal tibiofibular joint injury involving a separation of the fibular head from the respective articular surface of the lateral tibial condyle.

Epidemiology

Proximal tibiofibular joint dislocations are rare and account for less than 1% of all knee injuries in isolation. They are more common in association with other lower limb injuries ^1-5. It is one of the most frequently missed diagnoses ^1-3.

Associations

Proximal tibiofibular joint dislocations can be associated with the following injuries ^3,4:

• acute ankle injury or fracture
• lateral knee injury
• tibial shaft and/or tibial plateau fractures

Clinical presentation

Clinical symptoms include pain and tenderness of the fibular head, limited range of motion or weight-bearing difficulties ¹.

Complications

Proximal tibiofibular joint dislocations can lead to the following conditions ^1-5:

• persistent lateral knee pain with instability
• osteoarthritis
• peroneal nerve injury (more common with type 2-4)

Mechanism

Proximal tibiofibular joint dislocation is most often caused by internal or external rotational stress on a flexed knee ^1-5 which prevents additional support of the biceps femoris tendon and the lateral collateral ligament to the fibular head in this position ⁵.

Many dislocations are associated with plantar flexion of the foot. An alternative imaginable mechanism might be a direct blow to the lateral proximal lower leg or high impact trauma ².

Classification

According to the Ogden classification, proximal tibiofibular joint injuries can be classified into the following subgroups ^1-6:

• type 1: subluxation (more often in children and adolescents )
• type 2: anterior dislocation (most common ~85%)
• type 3: posteromedial dislocation
• type 4: superior dislocation

Radiographic features

Plain radiograph

Plain radiographs of the knee of the fibular head might show an anterolateral or posteromedial displacement of the fibular head in relation to the posterolaterally located tibial articular surface of the lateral tibial condyle. This includes a lack of or an excessive overlap of the fibular head with the lateral and/or posterior border of the lateral tibial condyle on anteroposterior and/or lateral knee radiographs ^2,4.

CT

Computed tomography can visualize the position of the fibular head in relation to the lateral tibial condyle in a multiplanar fashion and demonstrate proximal tibiofibular dislocation ^1,5.

MRI

In addition to malposition of the fibular head versus the proximal tibia, MRI can demonstrate injury of the proximal tibiofibular ligaments and any associated posterolateral corner injury as well as peroneal nerve injury ^4,5.

Radiology report

The radiological report should include a description of the following:

• location of the fibular head in relation to the tibial proximal tibiofibular joint surface
• proximal tibiofibular ligament injury
• signs or peroneal nerve injury

Treatment and prognosis

Management of proximal tibiofibular joint dislocation includes conservative measures like closed reduction and bracing or surgical approaches as closed or open reduction with internal fixation, the latter is usually performed in case of treatment failure or delayed diagnosis ^1,2. In case of associated distal tibiofibular syndesmotic injury, it should also include fixation ³. For post-reduction care, different periods of joint immobilization and gradual weight-bearing protocols have been proposed ⁵.

History and etymology

Proximal tibiofibular joint dislocations have been first described by the French physician Auguste Nelaton in 1874 ⁴ and were classified and extensively investigated by Ogden in 1974 ⁶.

Differential diagnosis

Conditions mimicking the clinical presentation or imaging appearance of  proximal tibiofibular joint dislocations include ^1,3:

• chronic proximal tibiofibular instability
• posterolateral corner injury of the knee
• proximal fibular fracture
• meniscal tears