Conditions or ailments that are the cause of a problem that you see - your observation.

Your vet may diagnose

Subchondral Bone Cyst, Generally

Synonyms: Osseous Cyst- Like Lesions


A cyst is a fluid filled structure, and subchondral means "under the cartilage." A subchondral bone cyst (SBC) is a hard fluid filled structure within the bone underlying the joint surface.

SBC's can result from a traumatic injury to the joint or from a developmental defect, in which the lining of the joint is infolded into the bone. Some SBC's cause lameness, while others do not. Whether or not they are a cause of lameness depends greatly upon their location, and whether the cyst underlies the weight bearing surfaces of the joint.

Sometimes, bone cysts are found incidentally on radiographs (during a purchase exam, for example), where they appear as a well defined dark spot within the white dense bone underlying the joint. The most common location for these cysts is the medial femoral condyle of the stifle, but they can be found anywhere.

Some SBC's are of little concern and require no treatment, while others may undermine the structure of the joint and cause collapse of the joint surface, resulting in arthritis and lameness. SBC's causing lameness are treated surgically using a variety of techniques. A more recent approach to treatment has been injection of steroids into the cyst, or injection of either PRP or stem cells into the defect.

my role

Questions To Ask Your Vet:
  • How do you know that the cyst is the cause of lameness?

Subchondral bone cysts may be part of the DOD complex of conditions (Developmental Orthopedic Disease) that affects young growing horses. The factors that reduce DOD may reduce the development of these cysts. Factors that may be involved include too much or too little exercise, nutritional imbalance, and excess energy in the feed ration of growing horses.

further reading & resources

Author: Doug Thal DVM Dipl. ABVP