Simmonds-Thompson test for complete Achilles tendon rupture
When the Simmonds-Thompson test, a calf squeeze, leaves the foot still, the Achilles tendon (the cord joining the calf muscles to the heel bone) is probably completely torn.
Remember
If squeezing the calf does not move the foot, the Achilles tendon is probably completely torn; an intact (joined-up) tendon makes the foot point downwards, and a partial tear gives weak movement.
Memory aid
picture the tendon as a puppet string
A healthy string pulls the foot down when the calf is squeezed, while a cut one leaves the foot still.
The Simmonds-Thompson test (also called the calf squeeze test) checks whether the Achilles tendon is still joined up. The tendon links the calf muscles to the calcaneus, the heel bone, and is also called the calcaneal tendon. Those muscles pull on the heel as they contract, pointing the foot downwards: this movement is called plantarflexion.
In the test, the patient lies face down (prone) with the feet over the end of the couch. The calf is squeezed towards the knee, and the response of the foot at the ankle tells you whether the tendon is intact. If the tendon is intact, the foot plantarflexes. A partial tear gives a weak movement. If the tendon is completely torn, a complete rupture, the pull of the calf is not passed down to the heel, so the foot does not move at all. No movement of the foot is a positive test.
A rupture often occurs during recreational sport. A typical story includes a sudden snap or pop at the back of the ankle, with swelling and a palpable gap (a dip you can feel with a finger) in the tendon.
A positive result has also been reported with an isolated tear of the part of the tendon that links the gastrocnemius (the large calf muscle) to the heel, so ultrasound or MRI can help when the picture is unclear.
Key facts
- Test
- the patient lies face down (prone) with the feet over the end of the couch, and the calf is squeezed towards the knee.
- Intact tendon
- the foot plantarflexes, which means it points downwards.
- Partial tear
- the movement is weak.
- Complete tear
- the foot does not move, and that is a positive test.
- Typical picture
- a sudden snap or pop, a palpable gap in the tendon and swelling, often during recreational sport.
- Imaging
- ultrasound or MRI can show the tendon if the examination is uncertain.
Exam traps
- Loss of dorsiflexion (lifting the foot upwards) does not point to a rupture, because the muscles at the front of the leg produce that movement and the calf squeeze does not test it.
- Normal plantarflexion on a calf squeeze goes against a complete rupture, because it shows the tendon is intact and passing the pull of the calf on to the heel.
- A weak response to the calf squeeze suggests a partial tear rather than a complete rupture, because some of the tendon still carries force to the heel.
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