What is Achilles tendon?

Achilles Tendon: Anatomy, Function, Injuries, and Rehabilitation

Introduction

The Achilles tendon is the strongest and thickest tendon in the human body, connecting the calf muscles to the heel bone. Named after the mythological Greek hero Achilles, this tendon plays a critical role in walking, running, and jumping. Despite its strength, the Achilles tendon is vulnerable to injuries, especially in athletes and active individuals.

In this article, we’ll explore the anatomical structure, function, common injuries, clinical assessment methods, rehabilitation exercises, and preventive strategies associated with the Achilles tendon.

Anatomy of the Achilles Tendon

Origin and Insertion

Structure

The Achilles tendon is composed of dense fibrous connective tissue with a high collagen content. It lacks a true synovial sheath but is surrounded by a paratenon, a sheath that allows some gliding movement and provides vascular supply.

Blood Supply

  • Mainly supplied by branches from the posterior tibial artery.

  • The midportion of the tendon has relatively poor blood flow, making it prone to degenerative changes and injuries.

Nerve Supply

Function of the Achilles Tendon

The Achilles tendon transmits the force produced by the calf muscles (gastrocnemius and soleus) to the heel, enabling:

Common Injuries of the Achilles Tendon

1. Achilles Tendinopathy

A chronic overuse injury characterized by degeneration of the tendon.

2. Achilles Tendon Rupture

A complete or partial tear, often seen in athletes.

  • Mechanism: Sudden dorsiflexion or pushing off forcefully

  • Symptoms: Sudden sharp pain, difficulty walking, inability to push off the foot

3. Paratenonitis

Inflammation of the surrounding sheath due to friction or overuse.

4. Retrocalcaneal Bursitis

Inflammation of the bursa located between the Achilles tendon and the heel bone.

Clinical Assessment

1. Palpation

  • Tenderness along the tendon, especially in the mid-portion or insertion

  • Swelling or thickening may be present

2. Thompson Test

  • Procedure: The patient lies prone with feet hanging off the table. The examiner squeezes the calf muscle.

  • Positive Sign: No plantarflexion indicates a ruptured Achilles tendon.

3. Range of Motion (ROM) and Strength Testing

  • Reduced active plantarflexion

  • Weakness compared to the unaffected side

4. Imaging

  • Ultrasound: Shows tendon structure and inflammation

  • MRI: For detailed visualization of tendon tears or degeneration

Rehabilitation and Physiotherapy

1. Acute Management

  • Rest, Ice, Compression, Elevation (RICE)

  • Heel lifts to reduce tendon strain

  • Pain relief with NSAIDs

2. Stretching and Strengthening Exercises

a. Gastrocnemius Stretch

  • Patient Position: Standing, one leg back with heel flat on ground

  • Procedure: Lean forward, keeping back knee straight

b. Soleus Stretch

  • Patient Position: Standing, one leg back, but knee slightly bent

  • Procedure: Lean forward to feel a stretch in lower calf

c. Eccentric Heel Drops (Alfredson Protocol)

  • Patient Position: On a step, heel hanging off

  • Procedure: Slowly lower the heel below the step level, then use the other leg to return to the starting position

  • Reps: 3 sets of 15, twice daily

d. Isometric Calf Contractions

  • Position: Seated or standing

  • Procedure: Contract calf muscles against resistance for 5–10 seconds

3. Functional Training

  • Progress to plyometrics, hopping, and running drills as pain allows

Preventive Strategies

  • Gradual increase in physical activity

  • Proper warm-up and stretching before sports

  • Avoid training on hard surfaces

  • Use of shock-absorbing footwear

  • Regular calf strengthening exercises

  • Addressing biomechanical issues such as overpronation

Associated Conditions

1. Haglund’s Deformity

Bony enlargement on the heel causing irritation of the Achilles tendon

2. Fabella Syndrome

Though rare, the fabella (a sesamoid bone behind the knee) may affect calf biomechanics and indirectly influence Achilles tendon stress.

3. Baker’s Cyst

A fluid-filled swelling behind the knee that can affect lower limb biomechanics, placing excess load on the Achilles tendon.

Conclusion

The Achilles tendon is a vital structure in the lower limb that bears immense loads during daily and athletic activities. Understanding its anatomy, function, and common pathologies is essential for early diagnosis and effective rehabilitation. Proper conditioning, biomechanical correction, and progressive rehabilitation play key roles in managing Achilles tendon disorders and preventing future injuries.

References


Location: India

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