Shin hernias in athletes: the connective tissue connection

A muscle herniation injury (technically referred to as a ‘myofascial defect’), is when there is a protrusion of a muscle through the surrounding connective tissue (fascia). In effect, muscle tissue that should remain sheathed and protected by the fascia poke through to the surface. The most common location of muscle hernias in active muscles is in the leg. However, because this type of injury is tricky to diagnose and rarely brought to the attention of medical professionals, there is actually relatively little data in the scientific literature about it^(1-3). In fact, the majority of early research on leg hernias (and much of our current knowledge today) stems from the efforts of military surgeons during the 1940s, detailing lower-extremity muscle hernias in military recruits undertaking strenuous exercise^(4-7).

How common are leg hernias?

Although it seems remarkable, the true incidence of leg hernias is not known. This is because many lower limb hernias are asymptomatic, and therefore remain undiagnosed because they are never brought to the attention of a physician or physiotherapist⁽⁸⁾. Of those lower-limb hernias that are diagnosed however, research has established that a tibialis anterior (TA – the muscle spanning the length of the shin bone) hernia is by far the most commonly involved muscle^(9-12). This is almost certainly because with little body fat under the skin of the shin and a solid bone behind, the fascia of tibialis anterior is particularly vulnerable to trauma – for example from a blow to the shin⁽¹³⁾. Having said that, it’s important to appreciate that although much rarer, other lower-leg muscle hernias can occur. These include hernias of peroneus brevis⁽¹⁴⁾, extensor digitorum longus⁽¹⁵⁾, gastrocnemius⁽¹⁶⁾ and flexor digitorum longus (see figure 1)⁽⁶⁾.