Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

1. Location and Structure

• The Achilles tendon is located in the posterior ankle.

• It is the strongest and thickest tendon in the body.

• Formed from:

  • Soleus muscle

  • Gastrocnemius muscle

• Inserts into the calcaneus (heel bone).

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2. Associated Bursae

Subcutaneous Calcaneal Bursa

• Located superficial to the Achilles tendon.

• Lies between:

  • Skin

  • Distal aspect of the Achilles tendon.

Subtendinous Calcaneal Bursa

• Located deep to the Achilles tendon.

• Lies between:

  • Achilles tendon

  • Calcaneus.

Clinical Relevance

• Inflammation of one or both bursae can cause:

  • Posterior heel pain

  • Posterior ankle pain.

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3. Vascular Supply and Watershed Zone

• The Achilles tendon has relatively poor vascularity.

• The watershed zone:

  • Area with the worst blood supply.

  • Located approximately 2 to 6 cm proximal to the calcaneal insertion.

  • Narrow in width.

• This area is prone to:

  • Tendinitis

  • Tendon rupture.

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4. Achilles Tendon Rupture

• Most ruptures occur above the calcaneal insertion.

• Frequently occur within the watershed zone.

• Rupture in this region may resemble pulling apart a rope.

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5. Epidemiology

• Often referred to as the “weekend warrior” injury.

• Typically occurs due to:

  • Overperforming

  • Overdoing physical activity.

• More common in:

  • Men aged 30 to 40 years.

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6. Mechanism of Injury

• Usually due to:

  • Eccentric loading

  • On a dorsiflexed ankle

  • With the knee extended.

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7. Functional Complaint After Rupture

Patients may report:

• One leg feels normal.

• The affected leg feels weak or problematic.

• Inability to stand on one leg on the affected side.

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Summary

• The Achilles tendon is the strongest tendon in the body.

• It inserts into the calcaneus and is formed by the gastrocnemius and soleus.

• The watershed zone (2–6 cm proximal to insertion) is prone to rupture due to poor blood supply.

• Rupture commonly occurs in active adults, especially men aged 30–40.

• Mechanism typically involves eccentric loading on a dorsiflexed ankle with knee extension.

• Posterior heel pain may also arise from inflammation of the associated bursae.