When people refer to the “back of the ankle,” they are pointing to a specific, highly functional anatomical area. The ankle is a complex structure that supports the body’s weight and provides the flexibility necessary for locomotion. This region is an intersection of powerful soft tissues and a major bone working together to facilitate movement. Understanding the names and roles of these structures helps explain why this area is prone to injury and pain.
Defining the Posterior Ankle Region
The most prominent structure defining the back of the ankle is the Achilles tendon, correctly termed the calcaneal tendon. This is the largest and strongest tendon in the human body. It serves as a thick, fibrous cord that connects the calf muscles—the gastrocnemius and soleus—to the heel bone. The heel bone is known as the calcaneus, and it provides the anchor point for the tendon.
Nestled between the calcaneus and the Achilles tendon is the retrocalcaneal bursa, a small, fluid-filled sac. This bursa acts as a cushion, minimizing friction and allowing the tendon to glide smoothly over the bone during ankle movement. Another potential bursa, the subcutaneous calcaneal bursa, lies immediately beneath the skin, but the deep retrocalcaneal bursa is anatomically more significant.
The Essential Role in Movement
The Achilles tendon and calcaneus form a powerful lever system that drives lower-body movement. The primary function of this muscle-tendon unit is to enable plantarflexion, the action of pointing the foot downward or standing on the toes. This action is executed when the calf muscles contract, pulling on the calcaneal tendon and lifting the heel.
This mechanism is fundamental to propulsion, the force needed to move the body forward during walking, running, and jumping. The Achilles tendon acts like a spring, storing elastic strain energy as the foot lands and releasing it to propel the body forward. When walking, the tendon handles forces up to four times the body’s weight. This load increases to over 12 times the body’s weight during activities like running.
Common Ailments of the Back of the Ankle
The high mechanical stress placed on this region makes it susceptible to several specific conditions, with Achilles tendinitis being one of the most frequent. This condition involves the inflammation or degeneration of the calcaneal tendon. Symptoms often include pain and stiffness in the back of the heel, especially upon waking in the morning. The discomfort may briefly lessen with light activity but returns with prolonged exertion, and the tendon may feel warm, tender, or appear thickened. Persistent pain that does not improve after a few weeks of rest warrants a consultation with a healthcare provider.
A more severe concern is an Achilles tendon rupture, a tear that can be partial or complete. This injury is accompanied by sudden, sharp pain and the distinct sensation or sound of a “pop” or “snap” at the back of the ankle. Following a rupture, a person will have difficulty walking normally and be unable to stand on their toes on the affected leg. They may also show a visible gap in the tendon. This injury requires immediate medical attention to determine the extent of the tear and the appropriate treatment, which may include immobilization or surgical repair.
Another common source of posterior ankle pain is retrocalcaneal bursitis, the inflammation of the fluid-filled sac between the Achilles tendon and the heel bone. Symptoms include pain, swelling, and tenderness at the back of the heel, which can make wearing closed-back shoes difficult. The bursa becomes irritated from overuse, repetitive strain, or pressure from ill-fitting footwear.
This bursitis can occur alongside, or be caused by, Haglund’s deformity, a bony enlargement on the heel. This deformity, sometimes called a “pump bump,” is an extra bone growth on the calcaneus that irritates the retrocalcaneal bursa and the Achilles tendon. People with high arches or a tight Achilles tendon may be susceptible to this condition, which is aggravated by the rigid backs of certain shoes. Treatment focuses on reducing inflammation through rest, ice, medication, and changing footwear, but persistent symptoms should be evaluated by a specialist.