Researchers have isolated an osteoarthritis biomarker, D-COMP (deaminated cartilage oligomeric matrix protein) that has seemingly conflicting effects: in the circulation, it marks degeneration in the hip joint, and in the cartilage, it provides an insight into joint repair.
Looking at 450 people who were part of the Johnston County Osteoarthritis Project, levels of D-COMP in the blood were linked with severity of osteoarthritis in the hip but not in the knee, and the levels were higher in cartilage near the damage caused by osteoarthritis compared with cartilage further away. Levels of the unaltered protein COMP in the blood were associated with severity of osteoarthritis in the knee but not in the hip, and levels did not vary in the cartilage.
According to the researchers, D-COMP is the first biomarker that is specific to a particular joint, and that its higher levels in the hip could be a marker for lower levels of repair in this joint. Conversely, its lower levels in the knee could suggest that the knee is better at repairing itself.
The next step in the research is to try to understand the difference between knees and hips and to use the same tools to analyze other joints, such as the ankle, for their levels of repair response.