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Although there is little hard evidence to support the belief, horseshoes have long been implicated as a cause of contracted heels in horses.

Researchers in Poland conducted a cross-sectional survey measuring the frogs of 114 horses in 22 stables and compared the results between shod and unshod horses. The frog width-to-length ratio was used as a measure of contraction with a value of less than 67% used to define the heels as contracted. About half of the horses had never been shod and half were regularly shod for at least the past year.

For the front limbs, about half (47-54%) of the barefoot horses were found to have contracted heels, while 69-82% of the shod horses were categorized as having contracted heels. In the hind limbs, only about 30% of the barefoot horses had contracted heels, while 44-58% of those shod in front only and 78% of those shod front and hind had contracted heels.

Although it is perhaps difficult to understand how shoes on front hooves would be associated with contracture of the hind heels, the authors emphasized that results of their statistical modeling suggested breed and unmeasured individual horse factors affect heel contracture more than the use of shoes. They concluded that heel contracture is a multifactorial problem, and this study disputed the popular opinion that shoes are an important cause of heel contracture.

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