VIEWS: 7 PAGES: 3 POSTED ON: 9/10/2011
THEFOOTMAN BY STEVE MANNING Foot types How to tell what type of feet you have. Shoe companies now make a wide variety of shoes. Each brand will have everything from soft, flexible, neutral shoes to shoes with maximum stability. While this means that there is now a shoe out there for even the more unusual foot, it also creates greater risk when buying shoes. It is now more difficult to buy the right shoe because there are so many shoes designed for feet other than your own. If you buy the wrong shoe you can become injured. You must first find out what type of feet you have before trying to find a shoe to suit them. While reading this article take off your shoes and have a look at your feet. Last Shape You can test the traditional foot type concept after a shower. Just have a walk on cement with wet feet and look at your footprints. In particular look at how much arch you have, and where a bisection of your heel passes through your forefoot and toes. If you have no arch to speak of then you have a flat foot. If there is a gap right the way through and the forefoot is not connected to the rearfoot then you have a high arch. If you have an arch but the forefoot and heel are connected by a band that is about 2cm wide then you have a so-called 'normal' foot. The heel print should be shaped like a rectangular oval. Draw a line straight down the centre of its long axis and extend it past the toes. If the line goes through the big toe or second toe then you have a straight lasted foot. If it passes through the outside two toes then you have a curved lasted foot. If it passes through the middle toe then you have a 'normal' foot. It is important to match your foot shape with a similar shaped shoe in order to get the best fit and support. Unfortunately this test is very limited because it only gives you a two dimensional image of your foot. It does not show how high your arch is at any spot where it is not touching the ground. Arch Shape Podiatrists make a cast of your foot when they are making a functional foot orthotic. They are trying to capture the special features of your arch height and shape that makes your foot unique. This is so they can build an orthotic made specifically for your foot alone. Off the Shelf orthotics and even the arches built into shoes can not do this. They are built on a generic foot shape that will fit some lucky people. When trying on shoes the size of the arch is not so important as where the arch is located. The peak of some people's arches is back close to the heel while others are more at the midfoot. They obviously will need different shoes with arches located in different positions. A recent update of a very popular shoe had the arch too far under the foot causing major blistering on the arch. These days the arch is built into the midsole more than the insole/sockliner and it is less forgiving for a poor match between arch shape and foot shape. The only way to tell if the arch is the right shape for you is to try the shoes on. They should feel like they offer even pressure to your arch over a wide surface area. If there are any pressure spots under your arch then they are likely to blister. You must run in the shoes to see what the pressure is like as you pass through the whole gait cycle, not just when you are standing. The key spots to look out for are along the inside border of your foot and just behind the joint of the big toe. Flexibility The most important but often overlooked factor in foot type is flexibility. We check general foot fle xibility by looking at how the arch changes from sitting to standing up. As a general rule the more flexible a foot is the more rigid a shoe it will need. The opposite is also true where the more rigid a foot is the more flexible a shoe it will need. The 1st Metatarsal-Phalangeal Joint. There are some special areas that we may test range of motion. The big toe joint, or first MTPj, is a common site of osteoarthritis. The result of this degenerative damage to the joint is limited flexibility known as Hallux Limitus. It is thought that around 60° of dorsiflexion (pushing the toe upward towards your shin) is required for normal walking. If the joint is not able to move this much then some other change to your gait is required. Sometimes this change is a rotational motion so you can roll off the side of your toe. This causes late stage pronation, a circular wear pattern under your forefoot and increased risk of injury somewhere else. Rigid shoes that can not flex under the ball of the foot make this condition worse. It is quite amazing to see somebody pronate more as they run in more stable shoes and to see the pronation disappear when they go to a soft flexible shoe. However this condition is tricky because it may be influenced and caused by rearfoot instability which still needs a stable shoe only in the rearfoot, to give adequate support. The Subtalar Joint. (STJ) The Subtalar joint is perhaps the most important joint in the foot. It is the joint just under your ankle between the talus and calcaneus. Most pronation and supination occurs at this joint. If it is highly mobile then pronation type of injuries are common. If it is too rigid then the foot cannot absorb the impact forces adequately and cushioning types of injuries are common. Pronatio n is a necessary and natural action, which has the purpose of displacing the shock sideways rather than up the leg. Most people pronate so most injuries are caused by over-pronation. But it is the ones who have limited pronation available that get the mo st injuries because their muscles and tissues must cope with the forces that should have been absorbed mechanically. The trick is to limit pronation in those people who are over-pronators, and to allow pronation in those with rigid subtalar joints. The biggest problem is that this can not be established by just looking at the degree of pronation that occurs. People who pronate a lot may have the supporting anatomy to cope with the pronation, while others who look like they are moderate pronators actually need anti-pronation control. You need to look at the injury and footwear history to determine which is the case. The Ankle Joint. The ankle joint requires a great amount of flexibility and strength. The ankle joint is between the leg bones and the talus. It must be very rigid sideways to prevent ankle sprains, but very flexible forwards and backwards so that the muscles can do their job in propelling you forward with the least amount of resistance. Again restricted dorsiflexion is the major problem. The body requires 5 to 10° of ankle dorsiflexion past perpendicular or the foot; knee or hip must take up the slack often causing injuries to them. Restricted ankle range of motion is called Equinus after a horses foot shape. It is often caused by tight calf muscles and can be partially relieved by a good stretching program. Some times joint damage or a bony block will prevent stretching from being effective. One of the common compensations is increased pronation at the subtalar joint as pronation has a dorsiflexion as well as eversion (tilting of the STJ inwards) and abduction (movement of the forefoot on the rearfoot outwards) component. The problem is that there is not much dorsiflexion available in comparison to eversion so pronation to end range of motion and beyond often occurs. One of the solutions is a heel lift in the shoe or wearing shoes with a high differential in height between the forefoot and rearfoot. This supports the foot in a position that reduces the amount of dorsiflexion required to toe off. Some Special Foot types There are a number of unusual foot types, which require special consideration when finding a suitable shoe. Like ankle Equinus they are mostly positional variations of the joints which affect gait and increase injury risk. Varus and Valgus Varus is the tilting out of the rearfoot against the ground when the subtalar joint is in neutral. Valgus is the opposite - tilting in. You can also have forefoot varus and valgus which is where the forefoot is rotated outwards or inwards in relation to the rearfoot. When these situations exist the foot must compensate for the positional variation in order to stand with the foot flat on the ground. Pronation will help compensate for a varus position but often the amount of pronation available to the STJ is limited. Supination may compensate for a valgus position increasing the chance of ankle sprains but sometimes rearfoot valgus increases pronational forces. This is particularly true if the problem is rigid rather than flexib le. Forefoot and rearfoot dual densities may help support these types of feet. Plantarflexed 1st Ray This is similar to forefoot valgus but it is just the big toe that is dropped down below the level of the other metatarsal heads. Sometimes it is a response to rearfoot varus as it is your big toe trying to reach the ground from an elevated position. If it is rigid then any extra pressure under the big toe joint or behind the joint, from a dual density midsole or orthotic may act like a block causing inju ry. HAV Hallux Abducto-valgus is the condition where the big toe is rotated and deviated inwards towards the lessor toes. This opens up the joint to damage. It also puts the big toe at a mechanical disadvantage, which is vital to an ideal gait pattern. A large bunion is often present at the big toe joint. Some shoes are wider over this joint and have removed the seams of the uppers to accommodate for the extra space needed. Pointy-toed shoes will increase the progression of HAV. Sometimes an instable rearfoot or midfoot will contribute to HAV so a stable shoe may be needed. Morton's Foot Short First Ray Morton's foot is where the second toe is longer than the first. This is primarily a fitting issue because if the length is OK for the big toe it may s till cause the second toe to buckle or lose its toenail. If the joint of the first toe is too short then your foot will fall inwards when you toe off causing late stage pronation. An anti-pronation shoe will not help this and some type of support may be needed to be made for inside the shoe instead. Coalitions If there is no flexibility at all at a joint then it may be a coalition. This is where the two bones have fused together. It can be the result of a genetic variation, joint damage, or an operation. Regardless of the cause the other joints will be put under greater pressure increasing their injury risk. The angle the joint is in has a big impact on which joints will be able to compensate. WHAT IS NORMAL? The idea that there are 'normal' feet and any variation on that is abnormal is not very valid. A better concept is to think of pathological (injury causing) foot types. There is a wide variation in human foot types and it is not relevant to say that one foot type is necessarily better than another. All that really matters is do you get injured because of the type of foot you have? Two people with the same foot type will not always both get injured. There are other factors such as muscle strength, recovery time, proprioception and tissue strength which are more important in injury prevention. After you find out your foot type it is time to find a shoe to suit it. We constantly see people who are injured simply because their shoes do not suit their foot types. I recommend that you go to a running specialist store to make sure you get the right advice on what shoes suit your type of feet. CASE STUDY: More is not better A young runner of about 60kgs came in complaining about his shoes causing injuries. They were straight lasted shoes with maximum stability. I had a look at his feet and they were quite flat and straight with only a small arch. After seeing his foot shape sitting and standing it was obvious that his arch did not change shape at all. I tested his range of motion at various foot joints and he proved to have a very rigid foot. While it was flat it was not collapsed into that position. He admitted he had always had flat feet but had really not had any injuries to speak of despite running nearly every day. He had purchased the shoes only two weeks before and since then had severe shin pain and sore feet. His physio had referred him on to us to check out his shoes. This was a classic case of getting the foot type wrong. Just because someone has a flat foot does not mean that they need more stability. This runner was born with a flatter foot. The key factor in his foot type was the fact that he had a rigid foot that needed a flexible shoe. After trying him in a light flexible shoe with a straight last he had immediate relief even while running outside the shop in them. Rigid feet have less ability to compensate for the shock of running by pronating. By adding even more pronation control you limit the compensation that is available even more causing excessive shock levels and injury.