Ankle Pain

The definition of an ankle sprain is an injury to the ligamentous support of the ankle. They are usually caused by sudden inward or outward twists of the ankle. The inversion (or lateral) ankle sprain is more common than the eversion (medial) ankle sprain because the lateral malleolus of the fibula extends further than the medial malleolus of the tibia. This offers more lateral support to the joint and forces the foot to invert. If the force applied to the medial side of the ankle is large enough, the medial malleolus can act as a fulcrum, forcing the lever, in this case, the foot, to invert even more.The everting muscles of the lower leg resist this exaggerated inversion, but when the opposing force is too large, the lateral ligaments get stretched or ripped, thus an inversion ankle sprain.

The ankle sprain, the lateral ankle sprain in particular, is the most common sports-related injury -- occurring mostly in sports involving running or jumping. The disability that this particular injury causes makes it a very important problem to be addressed by athletes, coaches, and athletic trainers. Understanding the physics of this injury is key to its prevention and rehabilitation. In order to understand the physics of this injury, we need to first understand the anatomy and function of the ankle joint including its bones and ligamentous support. We then need to understand the direction and magnitude of the forces applied to the joint at the time of injury. Once we understand the forces and where they are applied to the joint , we can see how this injury occurs and why it is so frequent. The talocrural joint, better known as the ankle joint, is comprised of the distal ends of the tibia and fibula ( the bones of the lower leg), the talus ( the highest foot bone), the articular capsule, the anterior talofibular ligament, the posterior talofibular ligament, the calcaneofibular ligament, the anterior tibiofibular, the posterior tibiofibular, the lateral talocalcaneal ligament, and the deltoid ligament. The concave surface of the distal end of the tibia fits into the convex surface of the trochlea of the talus. This particular method of articulation makes the ankle a hinge joint, and only permits motion about a single axis. The medial and lateral malleole, the easily palpable bony prominences on the sides of the ankle, prevent the talus from medial and lateral motion. The strong collateral ligamentous support and the hard malleole permits mostly plantar flexion ( pointing toward the ground) and dorsiflexion ( pointing toward the head), while limiting inversion (turning inward) and eversion (pointing outward).