Histology of two rice bodies isolated from the stifle of an adult draught horse stallion.

The researchers of this study have studied two ‘rice bodies’ found in the knee joint of an adult male working horse. These structures, similar to those found in human joints affected by rheumatoid arthritis, are degenerated parts of the joint lining and are believed to be a result of inadequate blood supply.

Understanding Rice Bodies

• The study begins by clarifying what rice bodies are. They are little structures found in the body’s joint spaces, much like grains of rice. While they are more commonly associated with conditions like rheumatoid arthritis in humans, they are less common in equine species.
• Rice bodies can emerge due to multiple reasons, but in this particular study they originate from degenerated synovial villi, the fronds or small tassel-like formations found within the synovial membrane of the joint. The synovial membrane is a type of connective tissue that surrounds the space within joints that aren’t fused together, ie. places where bones connect and allow movement.

The Findings in the Horse

• The study focused on an adult draught horse stallion, a large working horse, where two rice bodies were observed in the stifle joint. The stifle joint in horses is equivalent to the knee in humans, where the thigh bone, shinbone, and the kneecap interact.
• The surprising finding here is that the occurrence of rice bodies in equine species is uncommon. Typically, osteochondral fragments resulting from a bone and cartilage condition known as osteochondrosis dissecans are observed. However, in this case, the rice bodies were similar to those often seen in human arthritis patients.

Why the Rice Bodies Formed

• The research speculates that the formation of these rice bodies in the horse’s joint was induced by ischemia. Ischemia is a condition that happens when blood supply to a part of the body is restricted, depriving that area of necessary oxygen and nutrients.
• This lack of supply could have caused the synovial villi to degenerate, resulting in the formation of rice bodies. This explanation, however, is an inference made based on the histologic examination — microscopic study — of the structures, and other factors might have contributed to their formation as well.