Dancer's Tendonitis

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Original Editor - Puja Gaikwad

Top Contributors - Puja Gaikwad, Vidya Acharya, Wanda van Niekerk and Kim Jackson  

Introduction

The ankle is a crucial joint to acknowledge in the context of dance injuries because it is the connection between the leg and the foot that establishes lower limb stability. It is one of the most commonly injured body areas in dance. Incidences of injury to the ankle-foot complex scale from 27% to 49% of total injuries in ballet, modern, flamenco, and tap dancers. Dancer’s tendonitis is also referred to as Flexor Hallucis Longus tendonitis which is an overuse injury in which repetitive Plantarflexion and Dorsiflexion (pointing and flexing) of the foot results in inflammation of the FHL tendon.

In dancers, injury to the FHL is usually provoked by the recurrent movement caused by changing position from a plié position to a relevé position. (Plié is a French term meaning to bend, relevé, is a ballet term meaning “raised.” The term relevé explains the action when a dancer rises up on their toes). This movement of action produces a force that is ten times the dancer's body weight. Bio-mechanically, a restricted plantarflexion movement may lead to a prolonged pronated foot position when pushing off during the Propulsion Phase which can lead to FHL tendonitis.

The Flexor Hallucis Longus (FHL) has been also called as the ‘Achilles of the foot’ due to its unique role controlling midfoot pronation and supination, and its physiological and mechanical properties, which permit it to act as a powerful convertor of force from the rear foot all the way through to the big toe. Due to its anatomical arrangement and its unique actions, it is a muscle-tendon unit that can often become injured in athletic populations. This is often called the ‘dancers tendonitis’ because it is so prevalent in classic ballet dancers. However, it's going to affect any sport which requires repetitive push-off and extreme plantarflexion such as swimmers, sprinters, footballers, and gymnasts.

Relevant Anatomy and Biomechanics

The FHL arises from the posterior and distal two-thirds of the fibula, the interosseous membrane of the limb and to the intermuscular septa. It's distal and lateral to the muscle belly of the flexor digitorum longus (FDL) and deep to the soleus and gastrocnemius. It is pennate in shape and therefore the fibres of the muscle continue and converge on its tendon because it crosses the posterior surface of the lower tibia. The FHL tendon then passes posterior to the talus and deep to the medial retinacular structures at the posteromedial ankle. It is surrounded within a synovial sheath and passes through a fibro-osseous tunnel between the medial retinaculum and therefore the lateral tubercles of the talus. Because it turns to course towards the arch, it sits below the sustentaculum tali, which forms a horizontal sheath of bone on the calcaneus. The FHL is, therefore a part of the tarsal tunnel, and within the tunnel, it lies posterior to the neurovascular bundle. As the tendon of FHL moves through the arch of the foot, it crosses over the FDL tendon to lie on top of it. This is termed as the ‘knot of Henry’. At this level, the FHL is dorsal to the medial edge of the plantar fascia. This tendon continues to extend between the two sesamoid bones of the first metatarsophalangeal (MTP) joint where it is covered by the inter-sesamoid ligament, and inserts at the base of the distal phalanx of the great toe.

Injury to FHL occurs when the dancer is not fulfiling the natural requirements of movement through the joints. For instance,  when executing relevé it creates sickling and unstable foot positions because their forefoot is not strong enough and the limb external rotation and hip joint muscular support are not synchronous with the heel raises. In contrast, when executing plié, the result of poor control of weakened foot muscles is due to strain on the passive supporting structures, like the plantar ligaments, ankle joint capsules, and plantar fascia, etc. This result in faulty bone alignment, increased bone load, and risk of overuse syndromes in different tissues. Both these manoeuvers put tremendous strain on the ankles and feet because the bones are loaded in weight-bearing and the soft tissues must tether the bones sufficiently to control their positions and minimize the occurrence of injury.

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