Sounding a bit like something from the nether regions, the peroneals are actually a complex of 3 muscles that orientate along the outside border of the lower leg. Their primary job is to stabilise the lateral ankle, preventing inversion of the foot and ankle by producing an eversion force. The peroneal complex consists of the Peroneus Longus, Peroneus Brevis & Peroneus Tertius.

The two main peroneal muscles are the longus and brevis. Their tendons track around the lateral ankles and attach into the foot. The tendons are the weakest link between the muscle and the boney attachment. Both muscles prevent the foot and ankle from rolling outwards and the longus has an additional role in creating a "valgus" position of the forefoot, creating an optimal alignment to push off during gait. When the tendon and / or their tendon sheath becomes irritated and inflamed, pain occurs either along the tendon, or at the boney attachement. It is common to see swelling around the outside ankle when the peroneals are chronically inflamed (peroneal tendinopathy).  

Any excessive stress on the tendon/s can cause an inflammatory response within the tendons or the tendon sheath. The peroneal muscles are over worked when the foot is loaded excessively on the outside edge (a high arched foot & high heels), when the ankle is unstable or the foot is excessively rolled in (pronated). The peroneal tendons can also be significantly weakened and compromised following an inversion ankle injury. Common other stressors include worn-out footwear, high heels (especially stiletto / narrow heels), overly corrective orthotics, exercising on unstable ground, walking on soft sand and poor calf muscle strength.

A two pillar approach to treatment consisting of offloading and then strengthening, is imperative.

Firstly, identifying and eradicating the causative factor/s, then supporting the foot with valgus wedging at both the rearfoot and forefoot, is essential. The Emily Braidwood insoles are uniquely engineered to support the outside foot, from heel to toe, to offload both the peroneus longus and brevis from heel strike to toe off. This will offload the tendon to help resolve the inflammation and prevent reoccurrence.

Undertaking physiotherapy to progressively strengthen and condition the peroneal muscles, as well as the calf muscles, ensures the muscle can produce the required force and maintain endurance, thus protecting the tendon.  

Sometimes a tear of the tendon can be present, so if pain persists, seek imaging and medical assessment.