The Achilles tendon is the largest and strongest tendon in the human body, connecting the calf muscles to the heel bone. It transmits the force necessary to lift the heel for walking, running, and jumping movements. When the tendon shortens, known clinically as Achilles contracture or equinus deformity, it causes a restrictive tightening. This significantly limits the ankle’s range of motion, preventing the foot from moving freely and often leading to compensatory strain on other parts of the foot and leg.
Defining the Condition and Its Symptoms
The primary consequence of Achilles tendon shortening is restricted ankle dorsiflexion—the movement that pulls the top of the foot toward the shin. If the ankle cannot achieve a neutral angle, the heel cannot properly contact the ground during the gait cycle. This lack of flexibility forces the foot to compensate, resulting in noticeable physical symptoms.
Many individuals develop an altered gait, walking on their toes or the balls of their feet because the shortened tendon prohibits the heel from fully dropping. This abnormal weight distribution can lead to forefoot pain (metatarsalgia) and excessive strain on the plantar fascia. Calf pain and fatigue are also common, as the gastrocnemius and soleus muscles remain perpetually contracted.
The stiffness is often most pronounced first thing in the morning or following periods of rest. Simple actions, such as squatting or climbing stairs, become difficult. Wearing flat shoes, which require the most length from the Achilles tendon, often causes considerable discomfort. Diagnosis frequently involves the Silfverskiold test, which helps determine if the shortening originates in the gastrocnemius muscle or the entire calf muscle complex.
Primary Causes and Contributing Factors
Achilles shortening can result from congenital factors, such as genetic predispositions, or from various acquired circumstances. One common acquired cause is chronic lifestyle habits that keep the ankle in a plantar-flexed position. For example, the prolonged daily use of high-heeled shoes places the calf muscles and Achilles tendon in a continually shortened state, causing tissue fibers to adapt and restrict full lengthening when flat shoes are worn.
Sedentary behavior and a lack of physical activity also contribute to the contracture of the gastrocnemius-soleus complex. Conversely, a sudden increase in exercise intensity, especially running or jumping, can trigger overuse injuries. This leads to chronic inflammation and subsequent shortening of the tendon fibers, placing the tight muscle complex under excessive stress.
Immobilization of the lower leg, such as following an injury that requires a cast or prolonged splinting, can directly cause tendon shortening. Underlying medical conditions are also linked to Achilles contracture. These include systemic diseases like diabetes, which changes tendon structure, and neuromuscular disorders like cerebral palsy that result in muscle spasticity and weakness.
Non-Surgical Management and Therapy
Conservative treatment aims to restore the Achilles tendon and calf muscles to their normal length and flexibility through consistent therapeutic intervention. Physical therapy is a primary step, focusing on manual manipulation and a specific regimen of stretching and strengthening exercises. The goal is to gradually remodel the tendon and muscle tissue, allowing for greater ankle dorsiflexion over time.
Specific stretching techniques target the calf muscles. The standing wall stretch is widely recommended to lengthen the gastrocnemius, involving a lunge position with the back leg straight and heel pressed down. To focus on the deeper soleus muscle, the same stretch is performed with both knees slightly bent. Another effective exercise is the heel drop, performed on a step to intensify the stretch on the tendon.
Assistive devices are often incorporated to maintain the stretched position during periods of rest. Night splints are custom-fitted devices worn while sleeping that hold the ankle at a neutral or slightly dorsiflexed angle, providing a sustained stretch. Custom orthotics or simple heel lifts placed inside shoes can also help reduce immediate strain during daily activity. Consistency in performing these exercises, often for several months, is necessary for lasting increases in tendon length.
Surgical Intervention and Post-Operative Care
If conservative therapies fail and the equinus deformity severely impacts mobility, surgical intervention may be considered. The procedure depends on the extent of shortening and whether the restriction involves the gastrocnemius muscle or the entire complex. For less severe contractures, a gastrocnemius recession is performed, releasing the fascia and muscle fibers to allow lengthening without affecting the soleus muscle.
For more extensive shortening, an Achilles tendon lengthening procedure is utilized, often employing a Z-plasty technique. This involves making a Z-shaped cut into the tendon, allowing the surgeon to stretch and then suture the tendon back together at a longer length. Minimally invasive techniques, such as percutaneous or endoscopic lengthening, use small incisions to make partial cuts, relying on controlled healing to achieve elongation.
Following surgery, the ankle is immobilized in a cast or walking boot for several weeks. Patients are restricted from bearing full weight for six to eight weeks to allow the tendon to heal in its new position. A physical therapy program must follow, focusing on gait training and strengthening to prevent re-shortening and optimize functional recovery.