What is Achilles Tendonitis?

Achilles tendonitis (also known as Achilles tendinitis) refers to pain and inflammation of the Achilles tendon, which connects the calf muscles to the heel. Typically the condition is caused by overuse.

  • Approximately 10% of the running population experiences Achilles tendonitis[1]
  • Runners are 10 times more likely to experience Achilles tendon injuries than non-runners of the same age[2]
  • Approximately 30% of individuals who experience Achilles tendon injuries do not participate in strenuous physical activity[3]

Expert Insights

What is Achilles Tendonitis? - J. Carr Vineyard, MD


Tendons connect muscles to other bones. The Achilles tendon is the largest and strongest tendon in the body. It runs along the back of the lower leg, connecting the gastrocnemius and soleus muscles (calf muscles, also known as the triceps surae) to the calcaneus bone (heel bone) of the foot. The Achilles tendon is involved in plantar flexion of the foot (flexing the foot downward, away from the body) and is important for many activities such as walking, running, and jumping.

Detailed anatomical illustration showing the muscles of the foot and ankle highlighting the Achilles tendon

What is the Cause of Achilles Tendonitis?

Achilles tendonitis is a condition typically caused by overuse of the Achilles tendon. Repetitive strain on the tendon causes small tears, leading to pain and inflammation. Achilles tendonitis is not commonly the result of a sudden, specific (acute) injury.

There are two types of Achilles tendonitis, depending upon which part of the tendon is damaged:

  • Noninsertional Achilles tendonitis: the damage occurs in the middle portion of the tendon, above where it attaches to the calcaneus. This type of tendonitis typically affects younger, active individuals, particularly runners.
  • >Insertional Achilles tendonitis: the damage occurs to the lower portion of the tendon, at its point of attachment to the calcaneus. Bony growths (bone spurs) frequently develop with this type of tendonitis. This type of tendonitis can affect individuals of any age or activity level.
Anatomical illustration showing Achilles tendonitis

Other conditions affecting the Achilles tendon include:

  • Achilles tendinosis: chronic degeneration and thickening of the Achilles tendon that is not associated with inflammation
  • Achilles paratenonitis: inflammation of the covering (paratenon) of the Achilles tendon
  • Achilles tendon tear (rupture): occurs when the Achilles tendon is completely torn or detached from the calcaneus, and is most often the result of an acute injury

What are Risk Factors for Achilles Tendonitis?

Factors that can lead to Achilles tendonitis include:

  • A sudden increase in activity duration or intensity
  • Tight calf muscles
  • Running, especially long distances or on hard surfaces
  • Wearing unsupportive footwear
  • Age (the Achilles tendon weakens with age, making it more susceptible to injury)
  • Haglund’s deformity (abnormal bone growth on the back of the calcaneus)

What are the Symptoms of Achilles Tendonitis?

The symptoms of Achilles Tendonitis commonly include:

  • Pain and stiffness along the tendon after periods of inactivity, such as when waking up
  • Pain along the tendon and back of the heel during or following physical activity
  • Tendon is tender to touch
  • Swelling and warmth along the tendon

How is Achilles Tendonitis Treated?

Most individuals who suffer from Achilles tendonitis can successfully resolve symptoms through nonsurgical treatments such as:

  • Rest and activity modification, such as switching from high-impact to low impact-exercise
  • Ice and use of anti-inflammatory medication to reduce inflammation
  • Physical therapy focused on strengthening and improving flexibility in the calves
  • Use of supportive shoes or orthotics to reduce tension on the plantar fascia
  • Use of night splints to stretch the calf muscles while sleeping
  • Steroid injections to reduce inflammation
  • Shock wave therapy to promote healing of the Achilles tendon

Most individuals recover from Achilles tendonitis through nonsurgical treatment in approximately three months. In rare cases, surgical intervention may be necessary to address Achilles tendonitis that cannot be resolved with nonsurgical measures.

Surgery for Achilles tendonitis includes:

  • Debridement: surgical removal of damaged Achilles tendon tissue and bone spurs on the calcaneus
  • Gastrocnemius recession: surgical lengthening of the calf muscle (gastrocnemius) to reduce tension on the Achilles tendon

Surgery for Achilles tendonitis has very high satisfaction rates, with the majority of individuals experiencing symptom relief and improved function. Most patients who undergo surgery for Achilles tendonitis are fully recovered in 12 months.

Mazzone, M.F. & McCue, T. (2002). Common Conditions of the Achilles Tendon. American Family Physician. 65(9), 1805-1811. https://pubmed.ncbi.nlm.nih.gov/12018803/
Maffulli, N., Sharma, P., & Luscombe, K.L. (2004). Achilles tendinopathy: aetiology and management. Journal of the Royal Society of Medicine. 97(10), 472-476. https://doi.org/10.1258/jrsm.97.10.472
Last edited on February 9th, 2024 8:37 pm