What can you tell me about knee pain from an unstable tibiofibular joint? It’s at the top of my knee, not at the ankle. I guess those bones can be unstable at either or both ends. I just have knee pain along the outside of my knee and it’s been diagnosed as tibiofibular instability.

Pain along the outside or lateral knee can be caused by many things including tibiofibular joint instability. The tibiofibular joint is along the outside of the knee where the tibia (larger of the two lower leg bones) connects to the fibula (smaller of the two lower leg bones).

Some patients with this problem also report tenderness when pressure is applied over the fibular head. Instability usually tells us the joint is loose or shifts either into subluxation (partial dislocation) or into a fully dislocated position. This can be caused by small but significant anatomic variations.

Even slight changes that alter the natural angle of this joint can allow the fibula to slip out of the groove that holds it in place. Or a traumatic injury damaging ligaments and connecting soft tissue can damage the joint resulting in the same type of instability.

Instability may keep some patients from putting weight on that leg. The examiner compares the unaffected knee to the painful one and looks for changes in how the joint moves. Any unnatural shifts in the fibula as it moves against the tibia (called joint translation) will be evaluated with more specific clinical tests.

A tibiofibular joint that has been unstable for a long time can also cause knee popping, clicking, and catching. These symptoms are very similar to a lateral meniscal tear. The meniscus is a thick U-shaped piece of cartilage inside the knee joint. That’s why every effort is made to make sure the diagnosis is correct and the right treatment is applied. The use of X-rays, MRIs, and clinical tests are used to make an accurate diagnosis.