When it comes to lame horses, things aren't always simple–the injuries/problems don't always come one at a time. Take sidebone, for example–in a recent study presented at the 2010 American Association of Equine Practitioners Convention (held Dec. 4-8 in Baltimore, Md.) researchers described a series of cases with sidebone, coffin bone fractures, and associated soft tissue problems.

"The ungual or collateral cartilages in the foot (on either side of the coffin bone, thought to function in hoof expansion/shock absorption) start out as (soft) hyaline cartilage, then can ossify (harden into bone, termed sidebone or ossified collateral/ungual cartilage) with age or other factors," explained Kurt Selberg, MS, DVM, a veterinary resident at Colorado State University (CSU). "The causes are unknown, but might include concussion (from working on hard surfaces), ligament strain, poor farriery, or other factors. Clinical signs include a shortened stride and obscure lameness, perhaps because the ossified cartilages don't function in their normal expanding and contracting manner (with each step)