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What Is the Medial Malleolus?

The tibia, or shin bone, is one of the strongest weight-bearing bones in the body.
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  • Written By: Meg Higa
  • Edited By: A. Joseph
  • Last Modified Date: 19 November 2014
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The medial malleolus is the spherical bony protrusion on the inner side of the leg, just above the ankle joint. A similar protrusion on the outer side, called the lateral malleolus, is attached to the fibula bone of the lower leg. The former bulge is the terminal end of the tibia, or shin bone; both serve as anchor point for the ligaments and tendons that secure the foot to the leg. Although the medial malleolus is in a protected location and not particularly prone to traumatic injury, stress fractures that are sometimes overlooked can occur. Orthopedic doctors strongly recommend treatment of such micro-fractures.

In the leg, the medial malleolus begins flush with the tibia and tapers down and outward into a pyramid shape. The outer surface of the bone just beneath the skin is slightly convex; correspondingly, the inner surface in contact with both the tibia and the talus bone of the foot is concave. Attached to the coarsened — and slightly depressed — base of the pyramid is the deltoid ligament, which holds the ankle joint in place. The lateral malleolus is similar in shape and nearly identical in function.

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The two bones of the lower leg are the fibula and tibia. The latter, the larger of the two, connects the femur bone of the upper thigh at the knee with the talus bone of the foot at the ankle. On the lower back side of the fibula is the lateral malleolar sulcus, and on the back side of the tibia is the medial malleolar sulcus — vertical grooves along which a twin set of tendons nestles and extends to connect the foot. These critical tendons are partially covered and protected by the two malleoli.

Fracture of the medial malleolus is uncommon. The tibia is a necessarily strong bone, but excess stress from compression or torsion, such as landing from a jump or rolling an ankle, can cause trauma. Likewise, the bones of the foot are not immune to trauma. When such leg injuries occur, the likelihood that the medial malleolus also will have sustained a fracture is increased. It will vary in severity and type, the most common being a clean avulsion or a hairline stress fracture.

Of course, blunt force can cause the bone to chip. Fractures can sometimes result from running, jumping, sports that involve sudden change of direction or weight being repeatedly exerted on the ankle joint. Often, the pain, bruise and swelling of a micro-fracture dissipates relatively quickly, leaving a dull ache, sometimes also felt in the Achilles tendon. Tenderness might persist, "pins and needles" or numbness might be prominent, or pain might be felt only during certain types of movements by the ankle.

Treatment for a medial malleolus fracture is determined by it severity. A displaced fracture might require a prosthetic plate and cortical screws, and an undisplaced break might require only immobilization for several weeks. A stress fracture of the medial malleolus, if ignored, usually will worsen and require reconstructive surgery. If diagnosed and treated early, the prognosis for full recovery from most fractures is exceptionally good.

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