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.
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Prognosis & Relevant Factors
The prognosis is good in many cases, but it depends on the location of the SBC and damage to the joint.
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