Fabellofibular Ligament

ligamentum fabellifibulare

The fabellofibular ligament runs from the fabella (the sesamoid bone in the lateral gastrocnemius tendon) to the fibular head, forming part of the posterolateral corner complex of the knee. It is present in approximately 30% of individuals who have a fabella, which itself is present in approximately 15-30% of people. The ligament acts as a lateral static restraint complementing the popliteofibular ligament and the lateral collateral ligament.

Region: Knee

Biomechanics

Function & Actions

Reinforces the posterolateral corner of the knee when a fabella is present, providing an additional lateral restraint against varus and external rotational instability.

Clinical Relevance

Clinical Notes

The fabellofibular ligament and its associated fabella are relevant in posterolateral corner injuries where all static stabilisers may be disrupted. When the fabella is large and prominent, it can produce fabella syndrome with posterolateral knee pain from impingement against the femoral condyle during knee flexion. Fabella fractures occur rarely. In knee arthroplasty, the fabella within the gastrocnemius can be confused on radiograph with a loose body; post-arthroplasty fabella syndrome produces posterior knee pain and is managed by fabella excision.

Pathology

Common Injuries & Conditions

Posterolateral Corner Injury

High-energy varus and external rotation injuries disrupt the entire posterolateral complex including the LCL, popliteofibular ligament, and, when present, the fabellofibular ligament, producing varus laxity and a positive dial test requiring surgical reconstruction of all components.

Fabella Syndrome

A large fabella produces posterolateral knee pain and a palpable mass in the lateral gastrocnemius head that is painful with knee extension due to impingement against the lateral femoral condyle, treated by arthroscopic or open fabella excision when conservative management fails.