The Anatomy of the Ankle Joint

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The bony architecture of the ankle consists of three bones: the tibia, the fibula, and the talus. The articular surface of the tibia is referred to as the plafond. The medial malleolus is a bony process extending distally off the medial tibia. The distal-most aspect of the fibula is called the lateral malleolus. Together, the malleoli, along with their supporting ligaments, stabilize the talus underneath the tibia. The boney arch formed by the tibial plafond and the two malleoli is referred to as the ankle "mortise" (or talar mortise). The mortise is a rectangular socket. The joint surfaces of all bones in the ankle are covered with articular cartilage. (literature : Moore et al. (2010) pp.521-2)



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The ankle joint is a synovial joint. A synovial joint, also known as a diarthrosis, is the most common and most movable type of joint in the body of a mammal. As with most other joints, synovial joints achieve movement at the point of contact of the articulating bones. Synovial joints contain the following structures:
- Synovial cavity: all diarthroses have this characteristic space between the bones that is filled with synovial fluid
- Articular capsule: the fibrous capsule, continuous with the periosteum of articulating bones, surrounds the diarthrosis and unites the articulating bones; the articular capsule consists of two layers - (1) the outer fibrous membrane that may contain ligaments and (2) the inner synovial membrane that secretes the lubricating, shock absorbing, and joint-nourishing synovial fluid; the articular capsule is highly innervated, but avascular (lacking blood and lymph vessels), and receives nutrition from the surrounding blood supply via either diffusion (a slow process) or by convection, a far more efficient process achieved through exercise
- Articular cartilage: the bones of a synovial joint are covered by this layer of hyaline cartilage that lines the epiphyses of joint end of bone with a smooth, slippery surface that does not bind them together; articular cartilage functions to absorb shock and reduce friction during movement

What does a normal ankle look like on X-rays?

AAA Triple A® Ankle replacement AAA Triple A® Ankle replacement Articular cartilage does not show up on an X-ray. The presence of cartilage is presented by a space between the tibial and the talus bone (the joint space). On the X-ray here on the left, the bone looks smooth with no irregularities or loose bony particles.


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