Proximal Tibiofibular Joint Instability: An Underrecognized Cause of Lateral Knee Pain and Mechanical Symptoms

Abstract

Instability of the proximal tibiofibular joint is an uncommon and often unrecognized cause of lateral knee pain, mechanical symptoms, and instability. The condition results from one of three etiologies: acute traumatic dislocation, chronic or recurrent dislocations, and atraumatic subluxations. Generalized ligamentous laxity is a key predisposing factor for atraumatic subluxation. Instability of this joint may be in the anterolateral, posteromedial, or superior directions. Anterolateral instability is the most common type (80% to 85%) frequently occurring with hyperflexion of the knee with the ankle plantarflexed and inverted. Patients with chronic instability report lateral knee pain with snapping or catching often leading to a misdiagnosis of lateral meniscal pathology. Subluxations may be treated conservatively with activity modification, supportive straps, and knee-strengthening physical therapy. Chronic pain or instability is an indication for surgical treatment including arthrodesis, fibular head resection, or soft-tissue ligamentous reconstruction. Newly developed implants and soft-tissue graft reconstruction techniques provide secure fixation and stability with less invasive procedures and without the need for arthrodesis. Instability of the proximal tibiofibular joint (PTFJ) is an often overlooked cause of lateral-sided knee pain and mechanical symptoms. The differential diagnosis for lateral-sided knee pain and "snapping" is vast and includes meniscal injury, discoid meniscus, lateral collateral ligament (LCL) rupture, chondral injury, posterolateral rotatory instability, iliotibial band (IT) syndrome, and biceps tendinopathy. However, clinicians fail to appreciate PTFJ pathology when considering differential diagnoses for lateral knee complaints. PTFJ instability can be divided into three common etiologies: atraumatic subluxations, traumatic dislocations, and chronic dislocations. 1 Instability can be multidirectional, and its injury pattern can guide surgical and nonsurgical management options.