Thompson Test (Calf Squeeze Test) is the Most Reliable Bedside Test for Achilles Tendon Rupture
The Thompson test (also called the Simonds squeeze test or calf squeeze test) is the most reliable bedside clinical test for diagnosing acute Achilles tendon rupture, with a sensitivity of 0.96 and specificity of 0.93. 1, 2
How to Perform the Thompson Test
With the patient prone or kneeling on a chair with feet hanging free, squeeze the calf muscle firmly. A positive test (indicating rupture) shows absence of passive plantar flexion of the foot. An intact tendon produces visible plantar flexion when the calf is squeezed.
Recommended Diagnostic Approach
The AAOS guidelines recommend using two or more of the following clinical tests to establish the diagnosis 1:
- Thompson test (highest sensitivity at 0.96)
- Palpable gap in the tendon (sensitivity 0.73 when awake, 0.81 under anesthesia)
- Decreased ankle plantar flexion strength
- Increased passive ankle dorsiflexion with gentle manipulation (Matles test: sensitivity 0.88)
Key Clinical Pearls
The Thompson test is highly accurate for complete ruptures but unreliable for partial tears. Cadaveric studies demonstrate the test remains intact even with 25%, 50%, and 75% sectioning of the tendon, only becoming positive with 100% complete rupture 3. This is because the deep flexor tendons (flexor hallucis longus, flexor digitorum longus, posterior tibialis) can produce passive plantar flexion even when the Achilles is partially torn.
In all patients with confirmed ruptures, at least two clinical tests were positive 2. This underscores the value of performing multiple tests rather than relying on a single examination finding.
Common Pitfalls to Avoid
Pain and swelling can limit examination accuracy. When physical examination is equivocal due to patient discomfort or soft tissue swelling, point-of-care ultrasound can provide immediate diagnostic clarity 4.
Don't rely on the Thompson test alone for partial ruptures. The test's limitation in detecting incomplete tears means you need additional clinical findings (palpable gap, weakness, increased dorsiflexion) to make the diagnosis 3.
Imaging is not routinely necessary for diagnosis. The AAOS guidelines state there is insufficient evidence to recommend for or against routine MRI, ultrasound, or radiography to confirm the diagnosis when clinical examination is clear 1. However, imaging can be valuable when the clinical picture is ambiguous or to assess the extent of injury for treatment planning.
Clinical Context
The Thompson test combined with palpation for a gap provides the most practical and accurate bedside assessment. When both tests are positive in the appropriate clinical context (sudden pain during activity, feeling of being "kicked" in the calf, inability to stand on tiptoes), the diagnosis is essentially confirmed without need for imaging.