An ankle sprain occurs when the strong, fibrous tissues that connect bones, known as ligaments, are stretched beyond their normal capacity or torn. The vast majority of ankle sprains, estimated to be around 85%, involve the ligaments on the outside, or lateral side, of the joint, which is why most people associate a sprain with the ankle rolling inward. However, it is entirely possible to sprain the inside, or medial side, of the ankle. This medial injury affects a different set of ligaments and, while less frequent, can be significant and presents unique challenges compared to the more common outer ankle injury.
The Ligaments of the Inner Ankle
The stability of the inner ankle is primarily maintained by a large, triangular band of tissue called the Deltoid ligament complex. This structure is a collection of four distinct ligaments, connecting the medial malleolus, the bony prominence on the inside of the ankle, to several bones in the foot, including the talus, calcaneus, and navicular bone. The complex is notably thicker and stronger than the ligaments on the outer ankle, providing superior support against the foot rolling outward. The Deltoid ligament’s primary function is to prevent excessive eversion, or outward rotation, of the foot. This inherent strength is the main reason medial ankle sprains are much rarer, accounting for only about 10% to 15% of all ankle sprain cases.
Mechanism of an Inner Ankle Sprain
An inner ankle sprain, also known as a medial ankle sprain, occurs when the foot is forced into an extreme outward motion called eversion. This movement places immense tension on the powerful Deltoid ligament complex, causing it to stretch or tear. This mechanism is the opposite of the typical lateral sprain, where the foot rolls inward (an inversion injury) damaging the weaker outer ligaments. The force required for this injury is often greater than the force that causes the more common outer ankle sprain. Eversion sprains often happen in activities that involve a sudden, forceful shift in direction or when the foot is planted and an outside force pushes the lower leg inward.
Why Inner Ankle Sprains Are Less Common and Often More Serious
The Deltoid ligament’s superior strength means that when an injury does occur, the force involved is substantial, leading to a higher risk of associated damage. It takes a tremendous amount of stress to tear this thick ligament, and when that force is achieved, it frequently transfers to the surrounding bone and tendons. One potential complication is an avulsion fracture, where the ligament pulls a small piece of bone from the medial malleolus of the tibia at its attachment point. Injuries to the inner ankle are also often associated with damage to the posterior tibial tendon, which helps support the arch of the foot. Because of this high likelihood of concurrent bone or tendon damage, a medial ankle sprain is generally considered a more serious and complex injury than a simple lateral sprain.
Initial Steps and When to Seek Professional Help
Immediate care for any suspected inner ankle sprain should follow the R.I.C.E. protocol to manage pain and swelling. This involves resting the joint, applying ice for about 15 minutes every two hours, using compression with a bandage, and elevating the ankle above heart level. Avoiding heat and massage in the first 48 hours is also recommended, as these can increase swelling.
Due to the increased risk of an associated fracture or tendon injury, professional medical evaluation is strongly advised for all suspected medial ankle sprains. An inability to bear weight on the foot immediately after the injury or the presence of tenderness over the bony prominence of the medial malleolus are specific signs that an X-ray is necessary to rule out a fracture. Furthermore, if pain and swelling do not improve within a few days of conservative treatment, or if symptoms persist for more than a few weeks, further imaging like an MRI or CT scan may be needed to thoroughly assess the extent of the damage.