Achilles Tendon Rupture as a Diving Injury

As if divers didn’t have enough to think about when entering the water from a dive boat or dock, here’s another problem: if you don’t make a proper stride, you can rupture your Achilles tendon, which is a bad injury.

In a case reported by Jim Marwood in the South Pacific Journal of Underwater Medicine, as a diver stepped off with his left foot to make a giant stride, he felt a blow on the back of his left ankle. He began finning, but the ankle felt powerless. On return to shore, removing his left drysuit boot was painful. He could walk with a limp, but extreme pain prevented walking on soft sand. Although he had full, active ankle movement, he was unable to rise on the left forefoot. He had ruptured his Achilles tendon.

The diver was reasonably fit and had logged thirty-five giant stride entries in the past year, loaded, as he was on this occasion, with coldwater gear and heavy photographic equipment.

This time, however, a swell had caused the boat to roll. As he made his stride, he was unbalanced by the boat’s motion, and the process of shifting his weight removed support from his left heel. Because of his forward thrust and the boat’s motion, his left ankle was carrying a load of about 125 kg.

A direct blow may break the Achilles tendon, but about 60% of injuries occur when amateur athletes are pushing off with a straight leg. Obesity and sub-optimal fitness are predisposing factors. If you’re in the process of taking a giant stride off of a small step and the boat rolls, your risk of tearing the tendon is greater than if you had been stepping off a broad dive platform. And if you’re heavily laden, entry from a sitting position, while it might be less stylish, virtually eliminates the risk of ankle injury.

To determine whether an Achilles tendon has been injured, a test called the Thompson test requires the patient to lie prone with the knee up at a right angle. When the calf is squeezed firmly, an intact Achilles tendon will extend the ankle, while there will be no ankle movement if the tendon is broken.

Rapid treatment of injuries to the Achilles tendon is essential for optimum healing. A rupture requires surgical repair and weeks in a nonweightbearing, below-knee cast. The diver described in this incident still had difficulty supporting his weight on his left forefoot a year later.

— Ben Davison