Soft Tissues of the Foot
Bones are not the only important structures in the feet, there are also the muscle, ligaments and tendons to consider. The ligaments, tough collagen bands or straps, connect the bony structures and stabilise the foot, allowing all normal movements to occur within their tight restrictions. Capsular structures are present between all the foot joints, giving structural stability to the foot joints and allowing the lining of the capsule to secrete the nutritional and lubricating fluid the joints require. Straddling the foot arch longitudinally underneath is the plantar ligament, the largest ligamentous structure in the foot.
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.
Controlled falling is an interesting description of the complex art of walking we all manage so easily. Walking consists of a repeated cycle of standardised anatomical movements. When we stand our weight is distributed to the front and rear of our feet. When walking the heel strikes the surface at the back and outer edge and then the pressure moves forwards to the ball of the foot and to the big toe. Some of the stress is absorbed by stretching of the plantar ligament. Under the weight the arch flattens somewhat and the foot rolls inwards, allowing the foot to go into the position 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.
Problems with Gait
The body is an integrated whole so changes in one area can have knock on effects in another. An antalgic gait, a gait pattern employed with the aim of pain avoidance, is an example of a common gait anomaly. A neighbour I see regularly walks around holding his back very stiff and using just his legs to move. He glides about without the up and down and side to side movements typical in gait, trying to limit stresses in his back. With foot problems making a person have an abnormal gait this can stimulate problems in other body parts as they try hard to reduce stresses through the troubled area.
Babies' feet are cute and chubby and very mobile, being made up significantly of cartilage rather than bone initially, and it takes almost twenty years for the feet to become fully bony and growth completed. The foot arch is not obvious in the very young due to the thick pad of fat which fills up this area. As the child learns to walk the fatty cushion reduces and the arch reveals itself. Typically young children are often knock kneed to some degree up to the age of six with this process changing slowly with time until they have the normal knock knee of about seven degrees.
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.