Health & Fitness

Connecting across the two major bones of the navicular and the calcaneus and running under the talus is the spring ligament, a strong band-like structure which braces the foot arch. The weight of the body presses down to flatten the arch and the spring ligament holds between the two bones, becoming tauter as more weight is applied. Due to its great strength the spring ligament is adapted to manage the high forces generated by activities such as running, hopping or jumping, which are too vigorous for the musculature to able to hold the arch in place. The muscles contribute to arch maintenance but at a longer term lower level.

Accessory movements, small and almost unnoticeable internal joint movements, occur in the ankle as they do in the other synovial joints of the body. They occur naturally as the joint goes through its range of movement but we can’t perform them separately in isolation. If the joint loses a proportion or the entirety of its accessory movements some of the joint’s function will also be lost. An accessory movement of the talus in the ankle mortise occurs when the foot hits the ground and the forefoot and toes are flat, with the weight pressing down and inwards.

This slight twisting of the foot tensions it slightly and contributes to the elastic recoil as the weight begins to be lifted off the foot, added to by the stretch energy built up in the ligaments placed along the foot. As we step through this contributes a little pulse of energy to make things easier, often referred to perhaps as a spring in our step. To manage the challenges of rough surfaces the foot must adapt to different levels and angles, with much of this adaptation occurring at the subtalar joint below the talus and between it and the calcaneum.

Whilst the talus is solidly maintained within the ankle mortise the heel can move outwards and inwards underneath it by lateral movements of the subtalar joint, there being much less outward movement than inward. Our foot posture can vary depending on our walking patterns and this can interfere with normal foot function and precipitate painful conditions in the feet. For example lateral (outward) rotation of the feet makes us hit the ground initially with the outer border of the feet and forces the foot to roll significantly inwards to reach the ground each step.

As the foot rolls in this amount the arch tends to flatten, stretching the sling of supporting muscle tendons from the tibialis posterior and tibialis anterior muscles of the calf. This allows the talus to slip from its top position in the foot arch to some degree. As the forces involved in this medial rolling of the arch are very great this gradually over time makes the foot become abnormal when it performs like a static platform rather than a springy, dynamic part.

There is a greater range of movement in a medial (inwards) direction in the foot than in the lateral (outwards) direction which is limited by the fibula which gets in the way. This increases the likelihood of any sideways stresses resulting in a rapid inwards movement of the foot, causing an ankle sprain. Flat feet are often not painful in themselves but their abnormal position has knock on effects for all the joints above them including the ankle, knee, hips and low back. The forefoot also has a sideways arch even though this is small compared to the main foot arch, but if it flattens it places abnormal stresses on the head of the second metatarsal.

The lateral ligaments of the foot are the ones typically sprained due to the tendency of the ankle to go over as the foot moves forcibly inwards. The subtalar joint is always involved and damaged when there is a significant sprain of the ankle joint and this can cause instability of this area and lead to repetitive ankle sprains. Multiple sprains make the local tissues swell and this with time thickens up, turning into scar and giving problems if the ankle has been held still for some weeks in a cast, reducing both the stability and mobility of the area.

Jonathan Blood Smyth is the Superintendent of Physiotherapy at an NHS hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for physiotherapist in Blackpool visit his website.