The Achilles tendon is the largest tendon in the body, which allows us to push off with forces up to 10 times our body weight.
An Achilles tendon tear, or rupture, usually is a complete gap in the tendon 4-5 cm above the heel bone. The actual mechanism is commonly a rapid loading of an already-tensed tendon, e.g. lunging forward from a standing start.
Commonly it feels like being struck in the back of the ankle, followed by some pain. There often is no pain in this area before the actual tear. After the tear, symptoms range from pain and bruising to weakness in pushing off on the foot.
The Diagnosis is usually on clinical examination, with a gap being able to be felt in the tendon, a lax foot position and a calf squeeze test producing no ankle movement.