The Human Ankle " Part Two
The arch of the foot is also partly maintained by a strong ligament under the foot called the spring ligament, connecting the navicular with the calcaneus. It holds the arch together by resisting the tendency for the bones to separate under vertical stresses, becoming tighter the more weight is placed upon it. Due to its great strength the spring ligament is particularly useful when we are doing very vigorous movements such as running or jumping which might otherwise be too much for the muscle to resist the splaying of the arch. The muscles work more continuously at a lower level but between them and the spring ligament the talus is maintained at the top of the arch of the foot.
All the synovial joints in the body have accessory movements and the ankle is no exception. Accessory movements are little sliding or gliding motions which occur inside the joint normally during activity but which cannot be performed on their own. Joints need the accessory movements to function normally and a joint will lose some of its ability if these tiny movements are restricted or lost. An example is the inward slide of the talus in response to the vertical forces of the body as the toes and the forefoot are placed flat on the ground during stepping.
The foot twists during this manoeuvre, storing up tension energy which allows the recoil to occur in an elastic manner as the foot begins to lift off, a recoil which is supported by the longitudinal ligament stretch as the arch is flattened. From this we feel a little push of energy each step, very appropriately often referred to as the spring in the step. Rough ground presents challenges to the foot in terms of differing angles of surface and differing levels and the foot adapts to this with the subtalar joint, the joint between the calcaneum and the talus.
The sideways movements of the subtalar joint allow the heel to move inwards and outwards whilst the talus is still held securely in the ankle mortise, with much more inward movement of the heel bone than outward. There are various ways in which we can walk, in our foot posture, which can compromise the function of the foot and lead to painful foot problems. If the hips and feet are turned out as we walk this tends to make the outer border of the foot hit the ground first, meaning the foot has to roll inwards to hit the ground itself.
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.
The foot has greater ranges of movement in an inwards direction than outwards, the outwards seemingly blocked by the more anteriorly placed fibula if you try and turn your foot that way. This makes it more likely, if subjected to lateral instability, that the foot will turn rapidly inwards and cause an ankle strain. Although flat feet may not be painful in many cases, they can affect a whole series of joints above them from the ankle and knee to the hips and back. The sideways arch of the forefoot, a minor arch compared to the longitudinal arch of the foot, can also flatten and allow excessive weight to be borne by the second metatarsal head.
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.
All the synovial joints in the body have accessory movements and the ankle is no exception. Accessory movements are little sliding or gliding motions which occur inside the joint normally during activity but which cannot be performed on their own. Joints need the accessory movements to function normally and a joint will lose some of its ability if these tiny movements are restricted or lost. An example is the inward slide of the talus in response to the vertical forces of the body as the toes and the forefoot are placed flat on the ground during stepping.
The foot twists during this manoeuvre, storing up tension energy which allows the recoil to occur in an elastic manner as the foot begins to lift off, a recoil which is supported by the longitudinal ligament stretch as the arch is flattened. From this we feel a little push of energy each step, very appropriately often referred to as the spring in the step. Rough ground presents challenges to the foot in terms of differing angles of surface and differing levels and the foot adapts to this with the subtalar joint, the joint between the calcaneum and the talus.
The sideways movements of the subtalar joint allow the heel to move inwards and outwards whilst the talus is still held securely in the ankle mortise, with much more inward movement of the heel bone than outward. There are various ways in which we can walk, in our foot posture, which can compromise the function of the foot and lead to painful foot problems. If the hips and feet are turned out as we walk this tends to make the outer border of the foot hit the ground first, meaning the foot has to roll inwards to hit the ground itself.
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.
The foot has greater ranges of movement in an inwards direction than outwards, the outwards seemingly blocked by the more anteriorly placed fibula if you try and turn your foot that way. This makes it more likely, if subjected to lateral instability, that the foot will turn rapidly inwards and cause an ankle strain. Although flat feet may not be painful in many cases, they can affect a whole series of joints above them from the ankle and knee to the hips and back. The sideways arch of the forefoot, a minor arch compared to the longitudinal arch of the foot, can also flatten and allow excessive weight to be borne by the second metatarsal head.
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.
About the Author:
Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapists, physiotherapy, Physiotherapists in Windsor, back pain, orthopaedic conditions, neck pain and injury management. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.