The ankle plays an important role in the pattern of lower limb movements both in weight-bearing and non-weight-bearing positions.
Ankle movements: (Refer Fig 1)
- Plantarflexion (down)
- Inversion (inwards)
- Eversion (outwards)
Plantar flexion is the movement that describes the pointing of the toes toward the ground, as in standing on one’s toes.
Dorsiflexion is the opposite of plantarflexion and involves pulling the toes up as in walking on one’s heels.
Inversion is inward rolling of the foot towards the body’s midline and eversion is the exact opposite which involves outward rolling of the foot away from the midline of the body.
Joints in relation to movement
The ankle is made up of three distinct joints namely,
- Talo-crural joint (Ankle joint)
- Subtalar joint
- Distal Tibiofibular joint (High ankle)
Talo-crural joint (Ankle joint): It a hinge type of joint that allows movements of dorsiflexion and plantar flexion along one plane.The articulation of the lower ends of the leg bones and one of the tarsal bones (talus) forms the ankle joint.
Subtalar joint: The movements of Inversion and eversion take place at this joint. It lies beneath the ankle joint and is formed by the articulation between the talus and the calcaneal bone of the foot.
Distal tibiofibular joint (High ankle): This is a syndesmosis joint between the lower ends of the bones of the leg(tibia and fibula). A syndesmosis joint is a joint where the bones are connected by ligaments and have minimal movements.
Muscles that cause ankle movements
The muscles from the leg end as tendons that attach to the foot bones. They contract and transfer forces to cause a movement across the ankle joint.
- Outer muscles of the leg: The peroneal (Peroneus long and peroneus brevis) muscles are present on the outside aspect of the leg as shown in Fig 3. The contraction of the peroneal muscles help bend the ankle down moving the foot downwards (Plantar flexion) as in fig 3.
The peroneals also help to stabilize the big toe as it attaches behind it. It helps to lift the arch and plantar fascia to produce spring-like effect during running and jumping activities.
- Back muscles of the leg: The calf muscles (gastrocnemius and soleus) and the tibialis posterior muscles are present at the back of the leg as shown in Fig 4.
The calf connects to the heel bone by the Achilles’ tendon. When the calf muscles contract they moving the foot downwards (Plantar Flexion). The posterior tibialis help to turn the foot inwards (Inversion). They help to propel the body forwards as the foot pushes on the ground while walking.
- Front muscles of the leg: The tibialis anterior present in the front of the leg and attached in the front of the foot as shown in Fig 5.
The Tibialis anterior muscle pulls the ankle upwards (Dorsiflexion). It plays a role in striking the heel when you take a step forwards in walking.
Ligaments that support the ankle
Apart from muscles, the ankle is stabilized by many ligaments that surround the ankle.
- Lateral ligaments (outer ankle ligaments)
- Medial ligaments (inner ankle ligaments)
- High ankle ligaments
Lateral ligaments are present on the outer aspect of the ankle that are attached at the anterior (front), lateral (outer side) and posterior (back) parts of the ankle as shown in Fig 6.
- The Lateral ligaments play an important role to prevent excessive plantar flexion and inversion movements of the foot.
- Along with the medial ligaments, they also provide stability to the ankle during weight bearing movements.
Medial ligaments (Inner Ankle Ligaments)
The medial ligament otherwise known as deltoid ligament is present on the inner aspect of the ankle, as shown in Fig 7.
- The medial ligaments function as the main stabilizer of the inner aspect of the ankle against shear and rotational forces.
- They also act to support the inner arch of the foot.
Distal tibiofibular ligaments
The distal tibiofibular ligaments are located above the ankle and connect the high ankle syndesmosis joint as shown in Fig. 8.
- The high ankle ligaments ensure stability between the lower end of the tibia and the fibula.
- They resist any force that attempt to separate the tibia and fibula.
Risk of injury to the ankle
Any inflexibility in the ankle may cause inability to perform a movement properly. For example, poor ankle mobility due to tight soft tissue structures can reduce the range of movement at the ankle causing the knees, hips and trunk to over compensate. This may impair the ability of the trunk to load the joints properly hence increasing the risk an injury.