Achilles Tendon Rupture: Causes, Symptoms, and Treatment

What is the Achilles Tendon?

The Achilles tendon, also known as the calcaneal tendon, is the thickest and strongest tendon in the human body. It is composed of dense bundles of collagen fibers that are both extremely tough and highly elastic, connecting the calf muscles (the gastrocnemius and soleus) to the calcaneus (heel bone).

Its mechanical capacity is remarkable: research has shown that the Achilles tendon withstands forces equivalent to 3.9 times body weight during walking and 7.7 times body weight during running, making it one of the most highly loaded structures in the entire musculoskeletal system. It is indispensable for everyday movements including walking, running, and jumping.

Despite its exceptional strength and resilience, the Achilles tendon can tear or rupture when subjected to excessive, sudden, or repetitive stress. This injury most commonly affects athletes but can occur in anyone.

The hallmark symptom is the sudden onset of intense pain at the back of the heel, often accompanied by a characteristic loud snap or pop, and a near-immediate inability to walk normally.

The injury typically results from an acute traumatic event and/or from a tendinitis that has been neglected or inadequately treated. Diagnosis is primarily clinical, supported by imaging studies. Treatment may be surgical or conservative (casting/bracing), and with appropriate rehabilitation, gradual weight-bearing is typically possible within 4–6 weeks.

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Causes

Achilles tendon rupture occurs in approximately 1 person per 10,000 per year, and is most commonly seen in individuals who participate in sports involving explosive movements, rapid direction changes, or repetitive loading, including:

• Running and athletics
• Gymnastics
• Dance
• Basketball
• Tennis
• Volleyball
• Football and racket sports

The injury most frequently occurs as a result of a sudden, unprepared contraction of the calf muscles, for example at the start of a sprint or during a rapid push-off. This generates forces that briefly exceed the tendon’s tensile strength. Sprinters are particularly vulnerable at the moment of race start if the tendon has not been adequately warmed up.

Other Causes

Beyond acute sports injuries, Achilles tendon rupture can also result from:

• Direct trauma: falls with abnormal foot landing mechanics
• Neglected or inadequately treated Achilles tendinitis: chronic inflammation progressively degrades tendon fiber integrity, dramatically increasing rupture risk
• Certain medications that weaken tendon structure:
  • Fluoroquinolone antibiotics (e.g., ciprofloxacin, levofloxacin) are among the most commonly implicated, as they can disrupt collagen synthesis and matrix metalloproteinase regulation in tendon tissue.
  • Corticosteroids (both systemic and locally injected); repeated peritendinous corticosteroid injections are associated with a significantly elevated rupture risk.
• Metabolic conditions that impair tendon fiber quality:
  • Diabetes mellitus: advanced glycation end-products accumulate in collagen, reducing tendon elasticity
  • Obesity increases chronic mechanical overload on the tendon.
  • Hypercholesterolemia (elevated blood cholesterol): lipid deposits within the tendon (xanthomata) weaken its structural integrity. This association has been specifically documented in familial hypercholesterolemia.

Epidemiology and Risk Factors

• Achilles tendon rupture is 5 times more common in men than women
• The peak incidence occurs in men aged 30–40, the so-called “weekend warrior” demographic who are physically active but may not maintain adequate conditioning.
• Incidence is rising globally, likely related to increasing participation in recreational sports across older age groups

Key risk factors include:

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Symptoms

Patients with an Achilles tendon rupture typically describe a constellation of characteristic symptoms:

• Sudden sensation of a “blow to the ankle”: many patients report feeling as though they have been struck by an object or ball, even when no direct contact occurred
• Audible and/or palpable “snap” or “pop” at the moment of injury, a sound often described as loud enough for bystanders to hear
• Acute, severe pain at the back of the leg, in the region of the calf and heel
• Immediate difficulty walking: the ability to bear weight is severely compromised. In complete ruptures, walking is nearly impossible without significant assistance.
• Inability to plantarflex the foot: the patient cannot push the foot downward, as in pushing down a car pedal.
• Inability to stand on tiptoe on the injured foot, a simple but diagnostically important functional test
• Bruising and swelling localized to the heel and ankle, typically developing within minutes to hours of the injury
• A palpable gap or “dip” in the tendon, felt at the back of the ankle at the site of rupture (a highly specific clinical sign)
• Ankle stiffness and a subjective sensation of ankle instability

Complete vs. Partial Tears

The severity of symptoms correlates with the extent of the rupture:

• Complete rupture: all fibers are torn; symptoms are maximal; the palpable gap is typically evident; active plantarflexion is impossible
• Partial rupture: some fibers remain intact; pain and functional limitation are present but less extreme. The patient may retain some ability to plantarflex, albeit painful and weak.

Critical warning: While the pain of an Achilles rupture may paradoxically diminish after the initial event as the acute inflammatory response evolves, this does not indicate recovery. Many patients underestimate the severity of the injury and delay seeking medical attention, allowing the tendon ends to retract and making subsequent repair more difficult. Seek medical care immediately if you suspect an Achilles tendon rupture.

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Diagnosis

Diagnosis of an Achilles tendon rupture requires a formal orthopedic evaluation, combining clinical examination with imaging confirmation.

Clinical Examination

Medical History

The physician will enquire about:

• Mechanism of injury: what activity was being performed, and how exactly did the injury occur?
• Presence and character of the snap/pop sound
• Immediate and subsequent symptoms
• History of prior tendon problems, recent antibiotic use, or corticosteroid injections
• Relevant medical history (diabetes, hypercholesterolemia, autoimmune conditions)
• Level of physical activity and sporting demands

Physical Examination

Key examination findings include:

• Palpable gap in the tendon, typically located 2–6 cm above the calcaneal insertion (the zone of relative avascularity and greatest mechanical stress)
• Loss of resting tension: the injured foot rests in greater dorsiflexion compared to the uninjured side due to loss of calf-tendon continuity.
• Inability to perform a single-leg heel raise, a simple, reliable functional test

The Thompson (Simmonds) Test

The Thompson test (also known as the Simmonds test) is the most important and widely used clinical maneuver for diagnosing complete Achilles tendon rupture:

1. The patient lies prone (face down) on the examination table, with both feet hanging freely beyond the edge
2. The examiner firmly squeezes the calf muscles of the injured leg with both hands
3. Interpretation:
   • Normal result: squeezing the calf produces passive plantarflexion of the foot (the foot moves downward), indicating intact tendon continuity
   • Positive test (abnormal): squeezing the calf produces no foot movement, indicating a complete rupture of the Achilles tendon

The Thompson test has a sensitivity of approximately 96% and specificity of 93% for complete Achilles tendon rupture and is considered pathognomonic for this injury.

Imaging Studies

While the diagnosis can often be made clinically, imaging studies provide confirmation and additional information for surgical planning:

• Ultrasound: the most rapid, cost-effective, and widely available imaging tool for tendon evaluation. It can:

  • Confirm complete vs. partial rupture
  • Measure the gap between tendon ends
  • Dynamically assess whether the tendon ends approximate during plantarflexion (relevant for conservative management decisions)
  • Identify degenerative changes in the surrounding tendon tissue

• MRI (Magnetic Resonance Imaging): provides the most detailed anatomical assessment of the rupture, including the extent of tendon retraction, the condition of the remaining tendon, involvement of the tendon sheath, and associated soft tissue injuries. Particularly valuable for surgical planning and in atypical presentations

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Treatment

The optimal treatment strategy is individualized based on:

• Patient age and biological tissue quality
• Level of physical activity and sporting demands
• Extent and completeness of the rupture (partial vs. complete)
• Time elapsed since the injury (acute vs. delayed presentation)
• Patient preference and informed understanding of the trade-offs between approaches

Surgical Treatment (Preferred in Most Cases)

Surgical repair is the treatment of choice for the majority of patients, particularly those who are young, physically active, or wish to return to sport. It offers:

• Lower re-rupture rate: approximately 3–5% vs. 10–12% with conservative management
• Faster and more complete restoration of tendon strength and function
• Earlier return to sport and high-level physical activity

The procedure is typically performed under local or regional (spinal) anesthesia and involves:

1. A longitudinal skin incision along the posterior-lateral aspect of the ankle is positioned laterally to the midline. This placement avoids scar tissue over the area compressed by shoe counters, minimizing long-term footwear discomfort.
2. Identification and approximation of the ruptured tendon ends
3. Secure suturing using specialized non-absorbable suture techniques (e.g., Krackow, Bunnell, or modified Achillon techniques)
4. Layered wound closure

Minimally invasive and percutaneous techniques have been developed to reduce the risk of wound complications (the most significant drawback of open surgery) while maintaining the benefits of surgical repair. In appropriately selected patients, these techniques offer comparable biomechanical outcomes with lower complication rates.

Post-operative management:

• Immobilization in plantarflexion (foot pointing downward) for the initial healing phase
• Gradual progressive weight-bearing starting at approximately 6 weeks
• Full return to sport: typically 4–6 months post-operatively, following a structured rehabilitation program

Potential surgical complications include wound infection, sural nerve injury, skin necrosis (particularly in patients with vascular insufficiency or diabetes), deep vein thrombosis, and rarely, re-rupture.

Conservative Treatment (Casting or Functional Bracing)

Non-surgical management is appropriate for:

• Partial ruptures with maintained tendon continuity
• Older, less active patients for whom the risks of surgery outweigh the benefits
• Patients with medical comorbidities that significantly increase surgical and anesthetic risk
• Patients who specifically prefer to avoid surgery after informed counseling

Conservative treatment involves immobilization of the ankle in a below-knee cast or functional boot with the foot positioned in plantarflexion (heel elevated), allowing the ruptured tendon ends to remain in proximity for natural healing. The position is gradually adjusted to neutral over a period of 6–8 weeks.

Key advantages:

• Avoids surgical and anesthetic risks
• No wound healing complications

Key limitations:

• Higher re-rupture rate (~10–12%)
• Potentially longer time to full functional recovery
• May result in slightly reduced tendon strength and plantarflexion power at final outcome

Regardless of whether surgery is performed, physiotherapy rehabilitation is essential to achieving a successful outcome.

Physiotherapy Rehabilitation

A structured physiotherapy program is a non-negotiable component of recovery from Achilles tendon rupture, whether treated surgically or conservatively. A typical rehabilitation protocol progresses through several phases:

Typical recovery milestones:

• Walking without crutches: 6–8 weeks
• Return to light training: 3–4 months
• Return to full sport: 4–6 months (surgical) or 6–9 months (conservative, depending on the case)

💡 Key principle: The Achilles tendon requires progressive mechanical loading to remodel correctly. Immobilization and inactivity beyond the initial protection phase are counterproductive. A supervised, progressive loading program produces superior tendon healing outcomes.

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Can Rupture Be Prevented?

In many cases, an Achilles tendon rupture is preceded by a period of chronic tendon inflammation (Achilles tendinitis), whose symptoms include:

• Pain along the tendon and calf during and after activity
• Morning stiffness in foot and ankle movements
• Local swelling along the tendon course
• Tendon thickening: palpable enlargement of the tendon
• Bone spurs at the tendon insertion (Haglund’s deformity or calcaneal enthesophytes)

Recognizing and adequately treating tendinitis before it progresses to rupture is one of the most effective preventive strategies. If you experience any of the above symptoms, seek medical attention promptly rather than training through the pain.

Practical Prevention Strategies

1. Wear appropriate footwear for your sport and foot type. Shoes should provide adequate heel cushioning and support. Replace sports shoes before they become excessively worn, as deteriorated shock absorption increases tendon stress.

2. Always warm up thoroughly before training or competition. A gradual warm-up progressively increases blood flow to the tendon, improves collagen fiber alignment, and enhances viscoelastic properties, all of which reduce rupture risk.

3. Stretch and strengthen the calf muscles and Achilles tendon regularly. Eccentric heel drop exercises (the Alfredson protocol) have the strongest evidence base for improving Achilles tendon health and are the cornerstone of both prevention and tendinopathy rehabilitation:

   • Stand on the edge of a step with the heel off the edge
   • Lower the heel slowly below the step level using the injured leg only
   • Rise back up using both legs
   • Perform 3 sets of 15 repetitions, twice daily

4. Increase training load gradually: adhere to the “10% rule” (increase weekly training volume by no more than 10% per week) to allow the tendon time to adapt.

5. Cross-train with low-impact activities: alternate high-impact sports such as running with low-impact alternatives like swimming, cycling, or elliptical training to reduce cumulative tendon stress.

6. Avoid training on inappropriate surfaces: hard or uneven surfaces increase impact forces and lateral instability. Running tracks and grass surfaces are generally preferable to concrete.

7. Maintain a healthy body weight As discussed, excess weight chronically overloads the Achilles tendon. Even modest weight reduction significantly reduces tendon stress.

8. Monitor and manage blood cholesterol levels through a balanced diet. This is particularly important in patients with known hypercholesterolaemia or a family history of tendon xanthomata.

9. Exercise particular caution if taking fluoroquinolone antibiotics: discuss alternative antibiotic choices with your prescribing physician if you are an athlete or have a history of tendon problems. Also, avoid strenuous physical activity during and for several weeks after completing a fluoroquinolone course.

10. Seek early treatment for tendinitis: do not ignore early warning signs. Early intervention with physiotherapy, load modification, and, if indicated, extracorporeal shock wave therapy (ESWT) can prevent the progression from tendinitis to rupture.

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Sources and Bibliography

• Giddings VL, Beaupré GS, Whalen RT, Carter DR. Calcaneal loading during walking and running. Med Sci Sports Exerc. 2000;32(3):627-34. PMID: 10731005
• Bartolotta V, Taibbi A, Malizia G, et al. Real-time spatial compound sonography of Achilles tendon in patients with heterozygous familial hypercholesterolaemia and normal physical examination. La Radiologia Medica. 2007;112(4):562-71. DOI: 10.1007/s11547-007-0162-4
• Simmonds FA. The diagnosis of the ruptured Achilles tendon. Practitioner. 1957;179(1069):56–8. PMID: 13453094
• Thompson TC. A test for rupture of the tendo Achillis. Acta Orthop Scand. 1962;32:461–5. PMID: 13981206
• Thompson TC, Doherty JH. Spontaneous rupture of tendon of Achilles: a new clinical diagnostic test. J Trauma. 1962;2:126–9. PMID: 13920945
• American Academy of Orthopaedic Surgeons (AAOS) – Achilles Tendon Rupture
• Maffulli N et al. – Achilles tendon ruptures. Disability and Rehabilitation. 2008. PubMed
• Alfredson H, Pietilä T, Jonsson P, Lorentzon R. Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. American Journal of Sports Medicine. 1998. PubMed
• Lantto I et al. – Epidemiology of Achilles tendon ruptures: increasing incidence over a 33-year period. Scandinavian Journal of Medicine & Science in Sports. 2015. PubMed