Achilles Tendonitis is a common condition affecting the large tendon that connects the calf muscles to the heel bone. This tendon is heavily used during activities like walking, running, and jumping, making it susceptible to strain. When the tendon experiences repetitive stress without sufficient recovery, it can lead to irritation and degenerative changes in the tissue, resulting in pain and stiffness.
Understanding Achilles Tendonitis
Achilles Tendonitis, often referred to as Achilles Tendinopathy, is typically an overuse injury caused by repeated micro-trauma to the tendon fibers. This repetitive strain can result from a sudden increase in the intensity or duration of physical activity, or from having tight calf muscles that place extra tension on the tendon. The condition is characterized by a gradual onset of pain and swelling around the back of the ankle, which is commonly worse first thing in the morning or at the start of exercise.
The location of the irritation divides the condition into two main types. Non-insertional Achilles Tendonitis affects the fibers in the middle section of the tendon, typically a few centimeters above the heel bone, and is more common in younger, active individuals. Insertional Achilles Tendonitis occurs where the tendon attaches directly to the heel bone.
How Heel Lifts Provide Relief
Heel lifts, which are simple inserts placed inside the shoe, address the biomechanical strain on the Achilles tendon by mechanically shortening the calf muscle-tendon unit. By elevating the heel relative to the forefoot, the ankle is placed into a position of slight plantarflexion. This slight change in ankle angle reduces the maximum amount of stretch, or dorsiflexion, the tendon must undergo during the stance phase of walking or running.
When the heel is raised, the calf muscles—the gastrocnemius and soleus—do not have to lengthen as much to accommodate the movement, thus lessening the pulling force exerted on the Achilles. Scientific studies using ultrasound have confirmed that adding a heel lift, such as one measuring 12 to 18 millimeters, lowers the peak tensile load and strain experienced by the tendon during walking and running. For insertional tendinopathy, the lift also helps by limiting end-range ankle dorsiflexion, which can reduce the compressive forces that occur at the tendon’s attachment point to the heel bone.
When and How to Use Heel Lifts
Heel lifts are best viewed as a short-term, pain-modifying tool rather than a cure for Achilles Tendonitis. They offer passive pain relief, making activities like walking more comfortable, especially during acute flare-ups. For individuals with insertional Achilles Tendonitis, starting with a lift can be particularly helpful because it immediately reduces the irritating compressive force on the heel.
Practical application dictates that the lift should be used in both shoes, even if pain is only present in one ankle, to prevent an imbalance in gait and posture. However, prolonged, unsupervised use carries a risk of dependency and can contribute to further shortening of the calf muscles. Heel lifts should typically be trialed for a period of six to twelve weeks to assess their effectiveness for pain relief and should be gradually weaned off as the tendon’s capacity improves.
Beyond the Lift: Comprehensive Recovery
While a heel lift offers temporary relief by managing the load, it does not address the underlying issue of why the tendon lost its load-bearing capacity. Long-term recovery requires a shift from passive support to active strengthening of the tendon and muscle unit. The gold standard for this rehabilitation is a structured program of eccentric exercises, specifically slow, controlled eccentric calf raises.
Eccentric exercises involve contracting the calf muscles while they are lengthening, such as slowly lowering the heel from a tiptoe position over a step. This type of loading helps to increase the tendon’s strength, promote tissue remodeling, and improve its ability to handle strain. Alongside targeted strengthening, recovery also involves gradual load management, which means carefully monitoring and adjusting activities like running distance and intensity to prevent re-aggravation, and incorporating stretching for overall calf flexibility.