Which laboratory result is most characteristic of osteoarthritis?

Osteoarthritis is a degenerative joint disease characterized by the breakdown of cartilage and changes in the underlying bone. One of the key features of osteoarthritis is that the synovial fluid typically appears normal when examined under a microscope and is clear, indicating that there is no significant inflammatory process occurring in the joint.

The laboratory finding of a normal appearing aspirate on Gram stain and culture supports this idea. In osteoarthritis, the joint space is not typically filled with inflammatory cells as seen in conditions like rheumatoid arthritis or septic arthritis, and infection is not usually present. Therefore, the Gram stain and culture will not show significant findings, confirming the non-inflammatory nature of osteoarthritis.

This characteristic helps differentiate osteoarthritis from other forms of arthritis. Conditions that involve a high leukocyte count or presence of crystals in the joint fluid, such as gout or pseudogout, are indicative of inflammatory or crystal-induced arthritis. Likewise, low glucose levels in joint fluid are associated with inflammatory arthritides and infections. Hence, the observation of a normal aspirate suggests that inflammation is absent, which aligns with the pathology of osteoarthritis.