The Achilles tendon is the largest tendon in the human body and provides the attachment of the converged soleus and gastrocnemius muscles to the calcaneus. Achilles tendon ruptures often result from indirect trauma related to sports and exercise and primarily affect men between the ages of 30–50 years. Pre-existing degenerative conditions and certain drugs (e.g., local glucocorticoid injections) have been linked with an increased risk of complete or partial Achilles tendon rupture. Patients may experience a sudden onset of sharp pain in the tendon at the back of the ankle, usually accompanied by a popping or snapping sound or sensation. A positive Thompsons test may be followed by an ultrasound or MRI to confirm the Achilles tendon rupture. Both conservative and surgical treatments are recommended. Surgical treatment is associated with a lower risk of Achilles tendon re-rupture. However, complications linked to surgery, such as infection and hemorrhage, must be taken into consideration.
Anatomy of the Achilles tendon
- Largest tendon in the human body
- Provides the attachment of the converged soleus and gastrocnemius muscles to the calcaneus
Mechanism of injury
- Indirect trauma from physical activities (e.g., tennis, basketball)
- Rarely, direct trauma or longstanding paratenonitis (possibly with tendinosis)
- Pre-existing degenerative conditions (including polyarthritis)
- ↓ Physical conditioning (poor physical condition)
- Local injections of glucocorticoids
- Systemic glucocorticoids
- Fluoroquinolones 
- Complete rupture (most common)
- Less common
- Partial rupture
- Avulsion of the bony insertion of the Achilles tendon at the calcaneus
- Popping or snapping sound/sensation when the injury occurs
- Sudden, severe pain in the Achilles tendon
- Difficulty mobilizing: loss of plantar flexion power on the affected side
- Deformity: calf swelling; (e.g., hematoma) and/or palpable interruption of the affected Achilles tendon
- Clinical tests
Thompson test: squeezing the calf (e.g., gastrocnemius muscle) of the patient, in the prone position with legs extended
- Normal: results in passive plantar flexion
- Rupture: absent passive plantar flexion
Hyperdorsiflexion sign: the patient sits prone with knees flexed to 90°; both feet are passively dorsiflexed maximally.
- Normal: normal dorsiflexion of the affected leg
- Rupture: excessive dorsiflexion of the affected leg
- O'Brien needle test: a needle is inserted 10 cm proximal to the calcaneal insertion of the Achilles tendon; the foot is passively dorsiflexed.
- Thompson test: squeezing the calf (e.g., gastrocnemius muscle) of the patient, in the prone position with legs extended
Normal plantar flexion does not rule out a suspected Achille's tendon tear.
Always compare the symptomatic side with the opposite normal side.
- Mainly a clinical diagnosis
- Imaging is indicated to evaluate the extent of the injury and/or to exclude other suspected pathologies.
- Ultrasound (best initial test)
- X-ray: mainly to rule out suspected bone fractures
- MRI (confirmatory test): only imaging modality that can distinguish between a partial and complete rupture
Both conservative and surgical approaches are recommended, but the indications for conservative vs surgical treatment are controversial.
- Icing, rest, analgesia, serial casting
- Open or percutaneous tendon repair
- Re-rupture: in ∼ 5% of cases after surgical treatment and ∼ 10% of individuals after conservative treatment 
- Contractures and/or scarring → permanent limited range of motion
We list the most important complications. The selection is not exhaustive.
- Excellent prognosis with early treatment
- Repair of complicated cases (e.g., following re-rupture) has a poorer outcome.