Wednesday, April 15, 2009

Amazing Feet " Part Two

By Jonathan Blood Smyth

Soft Tissues of the Foot

The foot does not consist only of bones but also of tendons, muscles and ligaments. Ligaments are tough, relatively non-elastic straps or sheets which are designed to hold bones together. Ligaments allow the intended movements of the joint to occur and give the joint the stability it requires for normal function. Ligament capsules surround all the many joints of the foot, stabilising these joints and allowing the synovial lining inside them to secrete synovial fluid. The plantar ligament underneath and along the foot arch is the largest foot ligament.

The plantar ligament holds the arch in place to some extent and stores up energy when we are walking to use in the next step, giving us the spring in our step. A strain of the plantar ligament can be sharp and painful in the ligament and have knock on effects due to its supporting role. At the back of the heel is the Achilles tendon, a large and strong tendinous band which is a continuation of the fibrous tissue in the calf muscles, the soleus and gastrocnemius. The calf muscles provide propulsion in walking and running and allow us to stand on tiptoe.

Walking is a complex movement and often referred to as controlled falling. The gait cycle is the cycle we go through repeatedly with the same series of anatomical actions. The foot bears weight evenly on the front and rear on standing. In gait the foot hits the ground typically at the rear and outer border of the heel, the weight then passing forwards and towards the ball of the foot and the great toe. The plantar ligament stretches to some degree and absorbs some of the load. As the foot rolls inwards and the arch flattens to some amount, the foot moves into what is called pronation.

Supination is the next posture the foot moves towards as the midfoot hits the ground and starts to bear weight, the foot rotating outwards until the walker starts to push off on their toes so they can take their foot off the surface. In gait problems these postural movements can become exaggerated. Overpronation occurs when the foot turns in excessively and throws exaggerated forces across to the great toe which typically suffers sixty percent of the load in gait. If the person tends to bear weight along the outer, lateral border of the foot as they walk forwards the foot is said to be underpronated.

Difficulties with Gait

Changes which occur in one bodily area can have distant effects on other bodily regions due to the connected nature of body systems. A typical gait pathology is the antalgic gait, a gait where the body attempts to avoid a painful position or weight bearing posture. One of my neighbours attempts to minimise the forces which are being transmitted through his low back by gliding around smoothly, limiting spinal movement and using his legs almost exclusively to perform his gait. Pathologies can develop in other areas of the body as it attempts to limit forces by adopting an altered gait.

The foot does not become fully grown and fully ossified until about twenty years of edge and if we look at babies' feet we can see they are extremely mobile and chubby, being composed mostly of cartilage at that age. The arch of the foot cannot be seen easily as a thick fat pad sits in this region, gradually reducing with time and as the child learns to walk, allowing the arch to become noticeable. Knock knee is common in young children up until they are six years old, gradually becoming less pronounced until they settle around the normal level of about 7 degrees knock knee.

It's not until we are around twenty years of age until our feet are fully mature and fully ossified. Looking at the feet of young babies it is clear they are fat and bendy, with much of the internal skeleton being made up at this age of cartilage. We can't see any foot arch due to the fat deposits occupying this area and have to wait until walking commences before the fat reduces in size and we can observe the typical foot arch. Young children commonly also have knock knees but this tends to settle gradually by the time they are 6 years of age. The level of knock knee reduces gradually towards the adult level of seven degrees. - 14130

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