A tibiofibular joint is one of two articulations between the tibia and fibula, the two bones in the lower leg between the knee and ankle. These two bones meet at their topmost point just below the tibiofemoral or knee joint and at their bottommost point just above the talocrural or ankle joint. The upper articulation is known as the superior tibiofibular joint, or the higher of the two, and the lower articulation is known as the inferior tibiofibular joint, or the lower of the two. Both allow for very little movement between the two bones.
The superior tibiofibular articulation is a synovial joint known as an arthrodial or plane joint, which means that it allows a slight sliding movement between the two bones. This permits a very minor rotation of the lower leg below the knee, whereas the tibiofemoral joint only allows a hinge movement, or flexing and extending the knee joint. It is located where the lateral condyle of the tibia, the outermost of the two rounded bony protrusions on the top of the bone, meets the medial or innermost surface of the head of the fibula. These two flattened oval surfaces, joined by an articular capsule containing synovial fluid, glide slightly against each other during rotational movements. This tibiofibular joint is also held together by anterior and posterior, or front and back, ligaments.
At the lower ends of these two bones is the inferior tibiofibular joint, which is not a synovial joint but a syndesmosis. A syndesmosis is a type of articulation in which two adjacent bones are joined by an interosseous membrane rather than a synovial capsule. Along with symphysis joints, syndesmoses are classified as amphiarthrosis joints in that they allow only slight movement. Most motions produced by the ankle are achieved by its synovial talocrural joint, which hinges the ankle, and below that the subtalar joint, which rolls the foot inward and outward. The syndesmosis between the tibia and fibula, on the other hand, is more significant for holding the two bones together.
To help maintain and stabilize this joint’s fairly rigid structure, the inferior tibiofibular articulation is held together by four ligaments. The anterior inferior tibiofibular ligament (AITFL) crosses in front of the tibia and fibula bones; the posterior inferior tibiofibular ligament (PITFL) and transverse ligament connect the two bones from behind; and the interosseous ligament runs between the contiguous bony surfaces of the two bones. These ligaments’ inflexibility ensures that the integrity of the inferior tibiofibular joint is protected, but this rigidity also leaves them susceptible to high ankle sprains, a fairly common ankle ligament injury.