The malleolus refers to the distinct bony prominences on either side of the ankle. These palpable structures are anatomical landmarks that frame the ankle joint.
Understanding the Malleolus
A malleolus is a rounded bony projection extending from the tibia and fibula, the long bones of the lower leg. They form a part of the ankle joint, creating a secure socket for the talus bone of the foot. This arrangement allows for controlled movement while maintaining stability. The malleoli are essentially the flared ends of the leg bones that meet the foot.
Pinpointing Its Location on the Ankle
The malleoli are prominent bony protuberances on both the inner and outer sides of the ankle. The one on the outer side typically feels lower and more prominent than the one on the inner side. Their position helps define the ankle’s shape and guides foot movement.
The Specific Malleoli
The ankle joint features three specific malleoli, each originating from a different part of the lower leg bones. The medial malleolus is located on the inner side of the ankle. This projection is the distal end of the tibia, the larger of the two lower leg bones.
Conversely, the lateral malleolus is found on the outer side of the ankle. This is the distal end of the fibula, the thinner bone that runs parallel to the tibia. The lateral malleolus extends further down than the medial malleolus, which contributes to the ankle’s natural inclination.
A third malleolus, the posterior malleolus, is also part of the tibia. This projection is situated at the very back of the tibia, forming the posterior wall of the ankle joint.
Its Role in Ankle Stability
The malleoli play a primary role in forming the ankle joint and ensuring its stability. They create a strong, mortise-and-tenon-like joint with the talus bone of the foot. This arrangement securely cradles the talus, preventing excessive side-to-side motion.
The bony structures of the malleoli restrict lateral and medial displacement of the foot. This allows the ankle to primarily facilitate controlled up-and-down movements. Without these bony supports, the ankle would be susceptible to dislocation and instability during weight-bearing activities.
Common Malleolus Injuries
The malleoli are frequently involved in ankle fractures. A unimalleolar fracture affects a single malleolus, while a bimalleolar fracture involves both the medial and lateral malleoli. A trimalleolar fracture is a more complex injury, affecting all three malleoli: the medial, lateral, and posterior.
These fractures typically result from significant forces like twisting motions, falls, or direct impacts. Symptoms include severe pain, swelling, bruising, and an inability to bear weight. Seeking prompt medical attention is important if an ankle injury is suspected.