What Is Achilles Tendonitis?

In Greek mythology, Achilles was one of the greatest warriors of the Trojan War, known for his extraordinary strength. Yet, according to the legend, he had one vulnerable spot: his heel. The story eventually gave rise to the phrase “Achilles’ heel”, now commonly used to describe a person’s weak point.

Interestingly, the Achilles tendon is one of the strongest tendons in the human body - but it is also one of the most frequently injured. Connecting the calf muscles to the heel bone, it plays a crucial role in walking, running, jumping and pushing the foot off the ground. When this tendon is repeatedly overloaded or exposed to sudden changes in activity, it can develop Achilles tendonitis, more accurately known as Achilles tendinopathy.

Achilles tendonitis usually develops when the tendon is exposed to more mechanical load than it can currently tolerate. This does not necessarily mean excessive exercise; a sudden change after a period of inactivity can also place substantial stress on the tendon.

• A sudden increase in running, walking or sports activity

• Frequent hill running, sprinting or jumping

• Inadequate calf strength or flexibility

• Changes in training intensity or frequency

• Unsupportive or worn footwear

• Certain foot and lower-limb biomechanics

• Higher body weight

• Inadequate recovery between demanding activities

Persistent Achilles tendinopathy involves changes in the tendon’s structure and ability to tolerate load, rather than inflammation alone. This is why simply resting until the pain disappears may not always address the underlying problem.

Achilles tendonitis commonly causes pain and stiffness at the back of the ankle. Symptoms may initially appear only during or after physical activity and can become more noticeable as the condition progresses.

• Pain along the Achilles tendon or near its attachment to the heel

• Stiffness after waking or prolonged rest

• Tenderness when the tendon is touched

• Swelling or thickening around the tendon

• Pain during running, jumping or walking

• Difficulty performing a heel raise or pushing off the foot

Pain intensity does not always reflect the extent of changes within the tendon, so proper assessment is important when symptoms persist.

Achilles tendinopathy is generally classified according to the location of the affected tendon.

It develops where the Achilles tendon attaches to the heel bone. Pain is usually felt close to the heel and may worsen with footwear pressure or movements that compress the tendon against the heel.

It affects the tendon several centimetres above the heel bone. It is frequently associated with running and repetitive loading and may cause tenderness or thickening along the tendon.

Identifying the location matters because exercises and rehabilitation strategies may need to be modified accordingly. 

Diagnosis generally involves a medical history and physical examination. A clinician may assess the location of pain, tendon tenderness, swelling, ankle movement, calf strength and the ability to perform heel raises.

Imaging is not always required. Ultrasound or MRI may be recommended when the diagnosis is unclear, symptoms are atypical, another condition needs to be excluded, or a more detailed assessment of the tendon is required.

Treatment aims to manage painful loads while gradually restoring the tendon’s ability to tolerate activity. Complete inactivity is generally not necessary.

Depending on the severity and location of symptoms, treatment may involve:

• Activity modification: Temporarily reducing activities that significantly aggravate symptoms.

• Progressive strengthening: Gradually loading the calf and Achilles tendon is a cornerstone of rehabilitation.

• Physiotherapy: Exercise progression and movement strategies can be tailored to individual needs.

• Footwear adjustments: Appropriate footwear may help reduce aggravating forces.

• Heel lifts or orthotics: These may be useful in selected cases.

• Shockwave therapy: Consider this when symptoms persist despite rehabilitation.

Recovery is usually gradual. Tendons adapt slowly to changes in load, so rehabilitation often takes weeks to months, not days.

Progressive loading is central to Achilles rehabilitation. Depending on the individual and the location of the tendinopathy, exercises may progress from controlled calf contractions to double-leg and single-leg heel raises and eventually heavier strengthening.

The goal is not simply to stretch the Achilles tendon. It is to gradually improve its strength and capacity to handle everyday and sporting loads.

But exercise selection should be individualised, particularly with insertional Achilles tendinopathy, where certain positions can increase compression around the tendon’s attachment to the heel.

Persistent, worsening or recurrent Achilles pain warrants professional assessment. Sudden severe pain accompanied by a popping or snapping sensation, significant swelling or an inability to push off the foot can indicate an Achilles tendon rupture and requires urgent medical attention.

Early evaluation can also help distinguish Achilles tendinopathy from other causes of heel and ankle pain. Cannabinoid-based medications are also used for their potential role in pain management. Their use should therefore be considered only within an appropriate, clinician-guided pain-management plan.

Preventing recurrence largely comes down to managing tendon load. Training intensity, duration and frequency should be increased progressively, particularly after periods of inactivity. Maintaining calf strength, allowing adequate recovery and paying attention to changes such as increased hill running or jumping can also reduce unnecessary tendon stress.

Most importantly, returning to demanding activity should be based on the tendon’s improving capacity rather than simply waiting for pain to disappear.