Patient History

Clinical Presentation

The early recognition of instability in the proximal tibiofibular joint is necessary to optimize management of the injury and to avoid potential misdiagnosis. Early diagnosis of this injury can prevent further injuries to the joint that are harder to treat, such as chronic or fixed subluxation. Many common injuries can cause the same symptoms as proximal tibiofibular dislocation; therefore the integrity of the surrounding ligamentous structures should be investigated before a diagnosis is made. Proximal tibiofibular dislocation is commonly missed initially when high-energy trauma results in other traumatic fractures as well, such as injury to the tibial plateau or shaft, injury to the ipsilateral femoral head or shaft, ankle fracture, or knee dislocation.1,2

Atraumatic dislocation of the proximal tibiofibular joint is easily misdiagnosed when there is no clinical suspicion of the injury, owing to its association with a wide range of symptoms that mirror many common knee injuries. Patients with subluxation of the proximal tibiofibular joint commonly report pain over the joint that is aggravated by direct pressure over the fibular head. Flexing the knee to 90 degrees to relax the lateral collateral ligament and biceps femoris tendon, then moving the fibular head anteriorly and posteriorly, can test instability of the joint. Although many patients do not note symptoms during daily activities, symptoms may develop during activities that require sudden changes in direction. Patients often report symptoms such as knee instability and giving way during these activities, as well as clicking and popping during daily activities.³

Traumatic dislocations commonly cause pain along the lateral knee that radiates into the region of the iliotibial band and the patellofemoral joint and is increased with palpation of the prominent fibular head and ankle motion.⁴ The patient’s pain commonly limits the range of motion, especially knee extension, and motion of the ankle; the patient’s ability to bear weight on the affected leg is also limited by pain. It is common for patients to also have transient peroneal nerve injuries, especially with posteromedial dislocation.^1,2

Physical Examination Techniques

Suspicion of atraumatic injury to the proximal tibiofibular joint warrants extensive inspection during the physical examination of the knee. Most patient histories do not reveal any mechanism of injury to the proximal tibiofibular joint, and symptoms of lateral knee pain can be very misleading. The examination of patients with atraumatic subluxation or chronic instability should be performed with the knee flexed to 90 degrees. The proximal tibiofibular joint should be palpated for tenderness, and laxity should be evaluated by translating the fibular head anteriorly and posteriorly with the thumb and index finger and asking the patient if the symptoms are reproduced or if there is any apprehension.⁴ The stability of the proximal tibiofibular joint is typically increased by full extension of the knee; if it is not, the lateral collateral ligament and posterolateral structures may also be injured.

During significant trauma, traumatic dislocations of the tibiofibular joint are commonly missed, so the physical examination of this joint is a significant part of the comprehensive knee examination. The integrity of the ankle and functional status of the peroneal nerve should also be assessed during the physical examination, because of the association of nerve, syndesmotic ligament, and interosseous membrane damage with this injury. The relative avascularity of the area of the proximal tibiofibular joint prevents the presentation of knee effusion with an isolated injury, but there may be a prominent lateral mass.¹ Anterolateral dislocations often manifest with severe pain near the proximal tibiofibular joint and along the stretched biceps femoris tendon, which may appear to be a tense, curved cord.¹ Dorsiflexing and everting the foot, as well as extending the knee, emphasize pain at the proximal tibiofibular joint. The diagnosis of joint instability can be confirmed by steroid and local anesthetic injection into the joint under fluoroscopic guidance, if pain is relieved.

Imaging Techniques

The integrity of the proximal tibiofibular joint is best visualized through plain radiographs. Plain radiographs should be taken from anteroposterior, lateral, and oblique (45 to 60 degrees internal rotation of the knee) views, with comparison views from the contralateral knee, or from the preinjury knee if possible.⁵ When a diagnosis is suspected but not clearly established by plain radiographs, axial computed tomography has been found to be the most accurate imaging modality for detection of injury of the proximal tibiofibular joint.⁶ Magnetic resonance imaging (MRI) can also confirm a diagnosis of recent dislocation, based on the presence of pericapsular edema of the joint and edema of the soleus at its fibular origin of the popliteus muscle, but this finding is often absent in chronic and atraumatic cases.⁷