Sidebone occurs when areas of cartilage in the horse’s foot turn bony. You can feel the cartilages in the horse’s foot just above the coronary band towards the rear of the foot. When normal they are springy but as calcium is laid down in them they become hard. These changes may be caused by poor conformation in the foot or injury or possibly by mineral imbalance in the diet.
Sidebone does not normally cause lameness except occasionally when it is developing. Normally any inflammation settles down quickly with mild medication and some box rest may be necessary for a short while. Sometimes a side bone may fracture but will heal relatively easily in 2-3 months.