Biomechanics & Orthoses

Is usually congenital, but may be acquired as a result of injury, such as a broken leg. In such cases, where the legs may be of a differing length the foot of the longer leg will compensate by means of pronation - to attempt to 'level off' the disparity and make walking easier. Pronation in excess can lead to a host of problems; corn or callous formation, hallux-abducto-valgus (bunions) arch pain, plantar fasciitis, heel pain, general foot pain, ankle pain, Achilles tendon problems, knee pain, and hip and back problems.

Although all the above can result as a direct consequence of excess pronation, it is unusual for most people to experience more than 1 or 2 symptoms.

Many people suffer with foot problems, leg, knee and spinal conditions, because of the structure, or position of the feet during standing, walking or running.

In foot pronation of the heel rolls inward, the arch usually (but not always) flattens, and often the feet point outward. The opposite of this is supination, but this is less common. Excessive pronation or supination is usually congenital, but may be acquired as a result of injury, such as a broken leg. In such cases, where the legs may be of a differient length the foot of the longer leg will compensate by means of pronation - to attempt to 'level off' the disparity by wat of compensation and hopfully balance the body.

A functional device will allow normal foot pronation during gait. A functional, custom-fit device is made following a biomechanical examination. This is done by a podiatrist, the results of which enable him to determine the prescription and type of device to be made. Plaster of Paris casts of the feet are taken. These are then sent to a laboratory who specialise in the manufacture of orthoses. Because of this time consuming and expensive process, we issue temporary devices following an initial consultation. These are inexpensive and will give both the podiatrist and patient a good indication to long term orthoses benefit.

Many people suffer with foot problems, leg, knee and spinal conditions, because of the structure, or position of the feet during standing, walking or running.

During gait analysis the practitioner would look for head movement, position of the arms, trunk, pelvis legs and knee rotation. A close inspection of the feet and ankles would, of course take place.

The foot is composed of 26 bones, 16 intrinsic muscles, 33 joints, dozens of tendons and hundreds of ligaments.

All these components work together to give support, balance and mobility. The foot has to be a stable structure for standing, yet it has to able to adjust quickly during walking and running. During running and walking the foot must adapt to any uneven surfaces, by “unlocking” the bones. Then, in an instant during running and walking (just after midstance) it has to prepare for the propulsive phase of gait, here it must become a rigid lever, to enable it to propel itself and the lower limb forward.

There is kinetic chain of events that cause the body to move forward from the impact of landing, to the propulsive phase of gait that involve many bones of the lower limb. In sequence they are; the lumbar spine, pelvis, femur (thigh), tibia and fibula, the rearfoot; calcaneus & talus, the midfoot (or tarsus) and finally the forefoot; metatarsals and phalanges, or toes. Joints connect all these segments together, such as the knee which connects the thigh to the leg. There are many joints of the foot – each having a part to play in locomotion.

[Photo 6 - During walking (of a different subject) there is also pronation]

Bones, muscles, tendons and ligaments (of the lower limb) all work together act as shock absorbers, by rotation and compressions, and then move in opposite the direction prepare the limb for take off. Muscles are very important in that they initiate, and stop the movement and stabilise the limbs.

Walking, starts with the heel striking the ground, followed by mid-stance, then propulsion and toe-off. The rest of the time this leg and foot are in the ‘swing phase’.

Walking and running differ, in the main in that there is no double support phase (both feet in contact with the ground at the same time) and with running, both feet are off the ground at the same time and the body becomes airborne. During running the support phase is reduced to 30% of the gait cycle – compared with 60% in walking. Other differences in running include; more vertical movement, more flexion of the arms and at heel strike the foot moves up and toward the leg (dorsiflexion). It moves down in walking!

Injuries are thus more likely to occur in running than walking due to the increased stresses involved. One of the main reasons injuries happen is due to too much foot motion - pronation during the stance phase. Pronation is a necessary and vital part of gait, but too much can have a major impact on the other joints and muscles involved in gait. Excess foot pronation affects many people, and is characterised by in-rolling of the feet, low arch height, and out-toeing walking style.

Active Feet Sports podiatry has over 20 years experience in providing custom fitted foot orthoses to professional sports people and to patients with neurological problems alike.

We constantly review the latest technological advances in an ever changing field of podiatry and foot orthoses. In the last year we have studied the merits – and shortcomings of the vast majority of foot orthoses manufacturers and suppliers in the UK.

It is our belief that the orthoses we prescribe to our patients are the most advanced orthoses, being more controlling, comfortable and durable than anything seen before. However, no single type of orthosis (manufacturer) can be ideal for every patients’ needs and activity levels. Therefore, depending on each individual we would prescribe different devices from different manufacturers, using different materials to suit that patients’ needs the best.

Foot orthoses, when properly prescribed and manufactured will only be effective whist they are being worn. Depending on the patients’ condition orthoses should form part of an overall treatment plan, which may involve exercises, and other treatment modalities such as dry needling, physiotherapy or osteopathy.

It is essential that the correct shoe gear is worn. There are 3 basic training shoes types; neutral, stability and motion control. The structure of each depends on the curvature and rigidity of the last. Some mid-soles offer more stiffness on the medial side of the shoe to resist any pronatory forces from deforming the shoe. Cushioning is always compromised for control, ie a cushioned shoe will offer little support and a motion control shoe will offer little cushioning. If the wrong shoe is worn then the athlete is more susceptible to injury! This is a vital component of treatment and is in our repertoire of expertise which allows us to advise patients, especially if they have a sports related injury.

To claim that orthoses can cure all lower limb ailments is nonsense. Any sources suggesting this is the case should be ignored. There is nothing in any research literature to validate such claims. However, a properly prescribed orthoses and shoe can alleviate many symptoms and reduce risk of injury.

At Fulham Podiatry, CAD-CAM orthoses - Computer Aided Design – Computer Aided Manufacture are our preferred method of producing orthoses. We regard these devices as the way forward, as they offer more accuracy, have increased patient tolerance, they are more light weight and therefore have reduced space in the shoe compared to hand crafted devices.

The design is obtained by scanning the casts (taken by the podiatrist) of the feet, together with the biomechanical data, a numerically correct design is produced.

Using a specialised milling process the orthoses are direct milled from a solid block of high specification polypropylene, where design accommodations may be incorporated.

In some instances, such as gross excessive pronation, and some sports activities, there may be a need for a more forgiving material may be required. In such cases hand crafted devices, or devices made from a more flexible material (EVA) may be most suitable. The podiatrist will discuss this with you before making a prescription.