The lateral malleolus is the noticeable bony prominence on the outer side of the ankle. This structure is the lower end of the fibula, which is the smaller of the two bones in the lower leg. Its primary role is to provide stability to the ankle joint, working with ligaments and other bones.
Anatomy and Function of the Lateral Malleolus
The lateral malleolus is specifically the distal, or far, end of the fibula. It is shaped somewhat like a pyramid and is flattened from side to side. This bone forms the outer wall of the ankle joint, where it meets with the talus, one of the key bones in the foot. This junction is a part of the ankle mortise, the socket formed by the ends of the tibia and fibula that holds the talus.
This bone has several functions that contribute to ankle mobility and stability. It serves as an attachment point for three major ligaments on the outside of the ankle: the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament. These ligaments are bands of tough, fibrous tissue that connect the fibula to the foot bones, preventing excessive side-to-side movement. The lateral malleolus also acts as a pulley for the peroneal tendons, which run behind it and help control foot movement.
Common Lateral Malleolus Injuries
Injuries to the lateral malleolus are common, often resulting from twisting motions or direct impact. The most frequent injury is a fracture, which can occur from rolling the ankle, a fall, or trauma from an accident.
Another common issue is an ankle sprain, which involves the ligaments attached to the lateral malleolus. The force that causes a sprain can also stress the bone. Symptoms for both fractures and severe sprains are similar and include sharp pain on the outside of the ankle, swelling, and bruising. The area will be tender, and placing weight on the foot may be difficult or impossible.
Diagnosis and Treatment
Diagnosing an injury to the lateral malleolus begins with a physical examination by a healthcare provider. To confirm a fracture and understand its severity, an X-ray is the most common imaging tool used. X-rays can show if the bone is broken and whether the bone fragments have shifted out of their normal alignment, a condition known as a displaced fracture. For more complex cases involving ligament or tendon damage, a magnetic resonance imaging (MRI) scan may be ordered.
Treatment depends on whether the fracture is stable and non-displaced or unstable and displaced. For stable fractures, non-surgical treatment is often sufficient. This involves the RICE protocol: Rest, Ice, Compression, and Elevation, to manage pain and swelling. The ankle is immobilized using a special boot or a cast to allow the bone to heal, and crutches are used to avoid putting weight on the injured foot.
For unstable fractures where the bone has moved, surgery is necessary. The standard surgical procedure is called an Open Reduction and Internal Fixation (ORIF). During this operation, a surgeon makes an incision to access the broken bone, realigns the fragments into their proper position, and then secures them with hardware such as metal plates and screws. This internal hardware holds the bone together while it heals.
Recovery and Rehabilitation
The recovery period following a lateral malleolus injury varies based on the severity of the injury and the type of treatment received. Bone healing takes at least six weeks, but the full recovery timeline can be much longer. Patients are required to avoid putting weight on the injured ankle for several weeks, especially after surgery.
Physical therapy is an important component of the rehabilitation process. Once the bone has healed sufficiently, a physical therapist guides the patient through exercises to restore the ankle’s range of motion, strength, and balance. These exercises progress from simple movements to more demanding activities. Most people can return to their normal daily activities within three to four months, though mild pain and swelling can persist for longer.