Clues from Shoes
The evaluation and treatment of running injuries requires consideration of two not-quite-separate components. The first is the diagnosis of the exact nature of the injury (e.g., plantar fasciitis, runner’s knee, iliotibial band friction syndrome, etc.) coupled with the use of various measures to aid in the healing of the damaged tissue (ultrasound, massage, electrical stimulation…).
The second, and perhaps more critical, matter involves the determination of the underlying causes of the injury. To achieve this, the clinician has to be able to examine, analyze, and synthesize a variety of possible factors that may help explain the reasons a runner has “broken down.” This process is much like solving a jigsaw puzzle, with the “pieces” including factors such as training habits, postural alignment, gait dynamics, muscle balance and flexibility. While these are the leading items to be considered, there are times when examination of the wear patterns of an individual’s running shoes helps provide valuable clues in solving the mystery.
As in all areas of physical examination, to accurately identify the abnormal, we must first have a solid understanding of normal wear and tear patterns of shoes. For example, one of the most common misconceptions I have come across is the belief held by many runners that they must have some biomechanical problem since they wear out the outer half of the sole of the heel. In truth, this is a typical wear pattern, given the fact that normal running gait requires the foot making contact with the ground in a slightly supinated (inverted) position. As the heel lands on the outside edge and the foot then pronates (rolls inward) until the entire sole is on the ground, there is a certain amount of shearing, which causes wear and tear, that occurs due to friction between the outer half of the shoe sole and the road. Ground reaction forces also impart a good deal of compression to the mid-sole material of the shoe, causing the outside of the heel to “bottom out” more rapidly than the inner half, eventually giving the shoe a lopsided look.
Another area that sustains normal wear is the ball of the great toe. As the heel rises from the ground and the runner’s body is brought forward, most of the weight is borne by the inner aspect of the forefoot. Therefore, we can expect to see a greater amount of erosion of the sole in this area just as we see in the outer half of the heel. Of course, at both areas this wear should occur over a substantial period (500-600 miles) of running. If it develops much sooner, it could be indicative of a problem, but clearly, more significant problems would be indicated by wear in other areas of the sole, such as the inner half of the heel or outer border of the mid and/or forefoot.
There are other wear patterns that are good indicators of biomechanical problems. One of the most obvious is the broken down medial heel counter, the usually rigid material that cups the inside, back, and outside of the heel. Collapse of this section of the shoe most often signifies an exceptionally high degree of pronation at the rear and mid-foot. Given the technological advances in thermoplastic materials used in this area of the shoe, a breakdown here strongly suggests the need for orthotics for this individual.
Another telltale sign of trouble is a hole through the top of the upper material of the shoe caused by the great toe. This may indicate a lack of flexibility at the ankle, causing the great toe to be pulled upward more than usual as a compensation. Eventually, the upper (usually made of nylon mesh) wears through, which by itself is not typically a problem, but it can be a valuable clue when trying to explain the reasons for a particular injury.
These are just some of the clues from shoes that can be helpful in treating running injuries by providing additional information. In the grand scheme, they are usually one of the less significant factors to be considered, but sometimes this information is enough to confirm a working hypothesis.