Biomechanics of the Dancer’s Ankle and Foot

Original Editor - Carin Hunter based on the course by Michelle Green-Smerdon
Top Contributors - Carin Hunter, Jess Bell and Kim Jackson

Introduction

Assessing an injury in a ballet patient can be a daunting task. After gaining a basic understanding of the foot and ankle anatomy, applying biomechanical principles can help the therapist form a clear picture of the treatment plan. Dancers spend the majority of their time in extreme positions, especially plantarflexion and dorsiflexion of their ankle. If professionals (dancers and therapists) do not understand the requirements for these positions and the demands incurred, compensation can occur further up the kinetic chain, resulting in pain and injury.

The “Ideal” Anatomy for a Ballet Foot

While there is no "ideal" ballet foot, the following features could be considered optimal:

• Maximal plantarflexion in the talocrural joint
• Maximal dorsiflexion in the first metatarsophalangeal joint
• A medium arch
• A square foot where the first and second rays are of equal length could be considered the "best" foot shape for dancers
• Straight toes
• Strong intrinsic and extrinsic muscles
• Maximum flexibility, control, strength and endurance
• Ideally, a genetic aspect of some form of hypermobility

The "Ideal" Biomechanics for a Ballet Foot

• Ideal turnout, as a result of strong external hip rotators
• Strong flexible back
• Control and coordination of hypermobility
• Active stabilisation of the trunk
• Excellent ballet technique

Movements of the Foot and Ankle

Ankle

• Dorsiflexion
  • Required for plié
• Plantarflexion
  • Required for pointe work

Foot (excluding toes)

• Inversion
  • Excess inversion results in sickle foot (see image)
• Eversion
  • Excess eversion results in winged foot (see image)

Toes

• Dorsiflexion
• Plantarflexion
• Abduction
  • Often accompanies dorsiflexion
• Adduction
  • Often accompanies plantarflexion

The combination of movements across subtalar and tibiotalar joints causes supination and pronation.

Ankle ROM

Having sufficient range of motion (ROM) in the ankle joint is vital for the ballet dancer. Inadequate ROM can cause pain, compensation and injury.

Average ROM

The expected plantarflexion range of motion in an average human is 30-50 degrees, while the expected dorsiflexion range of motion with the knee extended is 10 degrees. When the knee is flexed, the expected range of dorsiflexion is 20 degrees. This results in an average through range measurement of 40 - 70 degrees.

A ballet dancer will work towards a through-range measurement of 90 degrees, with some reports of up to 101 degrees in elite dancers.

Important Aspects to Consider with ROM

• Degree of winging when pointing
• 'Over the box' movement in a pointe shoe
• Relevé height achieved

Due to the repetitive nature of ballet training and the need to be on pointe (i.e. a position of plantarflexion), a ballet dancer will often present with increased plantarflexion range. This tends to also cause a decrease in dorsiflexion, unless this is adequately trained. As a dancer advances in their discipline, this becomes a very common complication and needs to be addressed by treating professionals.

When a dancer advances in ballet and they move from demipointe positions to full pointe positions, it is also common to observe an increase in foot and ankle pain. A dancer needs to be educated on their foot biomechanics and understand that the main hinge point in their foot has to be the ankle joint. Thus, full range of motion is required at the ankle while the smaller joints in the foot often have to remain in a locked position.

“[Muscle strength] deficits contribute to faulty mechanics, including increased ankle inversion/eversion compensation in an effort to get en pointe/maintain position, decreased stability once there, knuckling under and decreased plantarflexion range of motion to allow ideal positioning over body over toes.”

Importance of Alignment

A strong, well-aligned foot supports alignment further up the chain. Poor alignment is a major risk factor for foot and ankle injuries in all ballet dancers, both recreational and professional. Good alignment is essential to improve control and strength, and to prevent injury in the ankle and foot.

Good Alignment

When en pointe and demi-pointe, our body weight is transferred down through the tibia to the talus. The talus forms a joint in front with the navicular bone, which in turn forms joints with the cuneiforms and with the 1st, 2nd and 3rd metatarsals and toes. Body weight should be more focused through the medial or inner three toes if the dancer is to transfer body weight forces correctly through footwear to the floor. Care needs to be taken to ensure that weight is taken through the 2nd metatarsal when moving through the foot or standing on demipointe/pointe. This will allow the 5 bones of the midfoot to “lock” ensuring the dancer has a more stable foot to work with. Engagement of the deep external hip rotators is key as turnout of the hip will lead to supination of the rearfoot (lifted arch position), which will also lock up the middle region of the foot.

In the “perfect” demipointe/pointe position, the centre of the ankle should be aligned with the dancer’s second toe. One visual cue that is relatively easy to use, and which can help both the teacher and dancer understand “right from wrong” alignment is as follows: The student is asked to locate and mark the mid point between the malleoli with a pen or marking pen.  A straight line is then drawn between this mark and the midline of the second toe. When standing on demipointe or pointe, this line should remain vertical.

Importance of Alignment for Calf Strength Development

Correct alignment of the foot, ankle, leg, hip and spine is essential for the correct engagement of muscles.

Incorrect alignment of the foot, ankle, leg, hip and spine can cause the dancer to try to force movements, potentially leading to an overuse injury of muscles that are not designed for dancing. The consequence of this is constant stiffness and tightness around the hip joints, thighs and calf muscles, which requires management.

Three Key Elements in a "Good" Ballet Foot

1. Arches

There are three arches in the foot:

1. Medial longitudinal
   1. Designed to allow the foot to trespass uneven surfaces and absorb shock
2. Lateral longitudinal
   1. Stability
3. Anterior transverse
   1. Aids in support and shock absorption, stability and balance, especially in relevé

These arches contribute to normal weight distribution, stability and distribution in dancing. The arches are formed by the tarsal and metatarsal bones. The shape allows them to act as a spring, bearing the weight of the body and absorbing the shock produced during dancing

The height of the arches is determined by the bone structure and influenced by muscles and the flexibility of ligaments. Arches in dancers' feet are commonly described as:

1. High
2. Medium
3. Flat

A medium arch is considered ideal. It allows good shock absorption, as well as flexibility as the ligaments are not so tight that they will restrict movement.

The Importance of Arches in Ballet

As mentioned above, the arches of the foot are important for optimal function, but for a ballet dancer, there are interesting complications to irregular arches.

• Weak lateral longitudinal arch
  • Contributes to sickling and supination
• Weak and flattened medial longitudinal arch
  • Contributes to winging and pronation
• Pronounced medial longitudinal arch
  • Results in supination or rolling to the outside of the foot

2. Intrinsic Foot Muscles

The most important role of the intrinsic foot muscles for ballet dancers is to oppose the clawing effect of the long flexors of the toes. When the toes are flexed at the metatarsal phalangeal joints, the action of the intrinsic muscles helps to keep the interphalangeal joints straight.

3. Plantar Fascia

Another key structure is the plantar fascia. The plantar fascia is a band of connective tissue that runs along the plantar or bottom surface of the foot. It acts as the main support for the medial longitudinal arch and, therefore, plays a key role in stabilising the foot in actions that require someone to push off the ground for propulsion (e.g. jumping or running).

Turnout

For a dancer to have good turnout, they need range and strength further up the chain. When this is not the case (e.g. a dancer does not have sufficient external rotation in the hips to enable correct turnout), we usually find THREE compensations:

1. Lower back
   1. A sway back posture, or lumbar hyperlordosis, combined with slightly flexed knees can cause an anterior pelvic tilt, greater hip flexion and the relaxation of the anterior capsule of the hip.
2. Knees
   1. A slightly flexed knee can allow increased external rotation of the lower limbs. This also increases the amount of grip required by the toes to maintain the position.
3. Feet
   1. Hyperpronation, as described below, can appear to increase turnout because of the abduction of the forefoot. This compensation causes increased tension in the lower back, knee and medial aspect of the foot.

Hyperpronation

Hyperpronation (i.e. excessive pronation of the ankle joint), often causes strain on the supporting structures, such as ligaments and tendons, on both the medial and the plantar aspects of the foot. This can lead to:

• Medial tibial stress syndrome
• Flexor hallucis longus tendonitis
• Plantar fasciitis
• Patellofemoral pain syndrome
• Retropatellar chondropathy
• Lower back pain

According to an article written by Nowacki et al., hyperpronation has also been found to contribute to the following conditions:

• Non-contact anterior cruciate ligament (ACL) injuries
• Sesamoiditis
• Achilles tendonitis
• Leg length discrepancies
• Stress fractures
• Hallux valgus
• Bunions