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The ankle

Dr Simon Kay looks at arguably one of the most sophisticated joints in the body

By Dr Simon Kay, GP

The ankle, or talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus bone in the foot. The articulation between the tibia and the talus bears more weight than between the smaller fibula and the talus.

The ankle and foot have two main functions: 1. To allow the distribution of force at the moment of heel strike 2. To provide a rigid level to allow a stable and propulsive phase of gait during walking and running (see Box 1 for more information).

The arrangement of the joints and bones of the foot means it is able to

BOX 1: THE GAIT CYCLE

The gait cycle is important to understand as any anatomical deviations in the individual may lead to abnormal movement patterns - commonly hyper-pronation.

Gait should proceed in the saggital plane with smooth movements. The key is the first metatarsal-phalyngeal joint, which acts as a pivot in the saggital plane, as long as the first ray is functioning correctly (great toe, first metatarsal and the first cuneiform).

The foot undergoes four key phases: 1. Support – the foot is in the neutral position 2. Propulsion – the foot starts to supinate, stiffen, by the joints locking

3. Swing – in non-weight bearing, the joints unlock to make the heel-strike pliable. The pliable foot hits and adapts to the ground 4. Heel strike - before the foot assumes the support role once again.

Figure 2: Main joints of the ankle and the movements associated with those joints (lateral view)

Intermediate cuneiform

Medial cuneiform

Navicular

Distal phalanx (5th toe)

Middle phalanx (5th toe)

Proximal phalanx (5th toe)

Fifth metatarsal

Lateral cuneiform

Talus Cuboid

Calcaneus

Figure 1a: The main bones of the foot (superior view)

accommodate not only smooth ground but also rough and uneven ground (see figures 1a and 1b). Eccentric and concentric movements of the shin muscles are used

Figure 1b: The main bones of the foot (superior view)

to control the movements of the foot during pronation and supination. Excess pronation can put a strain on the invertors of the foot ie. tibialis anterior,

Ankle joint – dorsi and

plantar flexion

Articulations of the

subtalar joint – inversion, eversion,

supination, pronation

Talus Navicular