Musculoskeletal · Orthopedics
The facts most likely to be tested
Achilles tendon rupture typically occurs in middle-aged men during stop-and-go sports involving sudden eccentric loading of the calf.
Patients classically report a 'pop' or the sensation of being 'kicked in the calf' at the moment of injury.
The Thompson test is the diagnostic maneuver of choice, where squeezing the calf fails to produce plantar flexion of the foot.
Physical examination reveals a palpable gap in the tendon and significant weakness in plantar flexion.
Fluoroquinolone antibiotic use is a major iatrogenic risk factor for tendon rupture due to collagen degradation.
MRI is the gold standard for confirming the diagnosis if the clinical presentation is equivocal, though the diagnosis is primarily clinical.
Initial management involves equinus splinting (plantar flexion) to approximate the tendon ends, followed by either surgical repair or functional bracing.
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A 42-year-old male presents to the urgent care clinic complaining of sudden, sharp pain in his left lower leg while playing recreational basketball. He describes hearing a loud 'pop' followed by an immediate inability to push off his foot. On physical examination, there is a palpable defect in the posterior ankle region. When the patient is placed in the prone position and the calf is squeezed, there is no plantar flexion of the foot. He has no history of trauma but was recently treated for a sinus infection with a 10-day course of levofloxacin.
What is the most likely diagnosis?
Achilles tendon rupture
The patient's presentation of a 'pop' during sports, a palpable defect, and a positive Thompson test (lack of plantar flexion on calf squeeze) is pathognomonic for an Achilles tendon rupture, with fluoroquinolone use serving as a classic predisposing factor.
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Etiology / Epidemiology
Occurs in middle-aged men (30-50) during stop-and-go sports. Fluoroquinolone use and corticosteroid injections are major risk factors.
Clinical Manifestations
Sudden 'pop' sensation followed by sharp pain. Thompson test is the pathognomonic diagnostic maneuver.
Diagnosis
Clinical diagnosis confirmed by MRI if the physical exam is equivocal. Ultrasound is a reliable, cost-effective alternative.
Treatment
Initial management is splinting in equinus (plantar flexion). Surgical repair is preferred for active patients to reduce re-rupture rates.
Prognosis
Re-rupture rate is 5-10%. Nerve injury (sural nerve) is a primary surgical complication.
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Epidemiology & Etiology
Predominantly affects males aged 30–50 years, often referred to as the weekend warrior syndrome. Chronic fluoroquinolone therapy and local corticosteroid injections significantly weaken the tendon matrix. Systemic conditions like gout or hyperparathyroidism may also predispose patients to spontaneous rupture.
Pertinent Anatomy
The Achilles tendon is the strongest and thickest tendon in the body, formed by the confluence of the gastrocnemius and soleus muscles. It inserts into the posterior aspect of the calcaneus. Its watershed area, located 2–6 cm proximal to the insertion, is the most common site of rupture due to hypovascularity.
Pathophysiology
Rupture typically occurs during eccentric loading, such as pushing off with a weight-bearing forefoot while the knee is extended. Degenerative changes, including tendinosis and collagen fiber disarray, often precede the acute event. The sudden mechanical failure results in a complete loss of plantar flexion power.
Clinical Manifestations
Patients report a sudden, intense pain often described as being 'kicked in the calf'. Physical exam reveals a palpable tendon gap and weakness in plantar flexion. The Thompson test is positive if there is no foot plantar flexion upon squeezing the calf muscle. Avoid weight-bearing immediately to prevent further retraction.
Diagnosis
The diagnosis is primarily clinical based on the Thompson test and the presence of a palpable defect. MRI is the gold standard for surgical planning to assess the degree of retraction. Ultrasound is highly sensitive for identifying the rupture site and measuring the gap distance.
Treatment
Initial treatment involves equinus splinting to approximate the tendon ends. Surgical repair is the first-line choice for young, athletic individuals to minimize the 5-10% re-rupture risk. Avoid aggressive early mobilization to prevent hardware failure or wound dehiscence. Conservative management with serial casting is reserved for sedentary patients.
Prognosis
Most patients return to pre-injury activity levels within 6-12 months. Sural nerve injury is a common complication of surgical intervention. Long-term monitoring for calf atrophy and persistent weakness is essential during physical therapy.
Differential Diagnosis
Achilles tendinitis: pain is gradual, not sudden, and the Thompson test is negative.
Plantaris muscle rupture: Thompson test remains negative and plantar flexion strength is preserved.
Calf strain: Thompson test is negative and the gap is absent.
Ankle fracture: localized bony tenderness rather than mid-tendon gap.
Deep vein thrombosis: calf swelling and tenderness without a palpable tendon defect.