Decreased synovial fluid lubrication linked with cartilage damage

A preclinical study suggests reduced synovial fluid lubrication may be common in both acute and chronic inflammatory conditions.

Inflammation resulting from knee injuries may lead to progressive loss of joint lubrication, predisposing patients to arthritis, a new study suggests.

Gregory D. Jay, MD, PhD, an associate professor of emergency medicine at Brown University in Providence, R.I., conducted the study with colleagues at the University of Rhode Island and at Case Western Reserve University School of Medicine, Cleveland. They published their results in Arthritis & Rheumatism.

Using a rabbit model, the researchers transected the anterior and posterior cruciate ligaments of 10 knees. They then aspirated synovial fluid from the affected knee joints weekly for three weeks. Analyses of the synovial fluid included quantification of concentrations of lubricin, Type II collagen peptides, C-terminal neopeptide 9A4 and keratan sulfate epitope 5-D-4. The researchers also measured elastase activity spectrophotometrically, according to the study.

The researchers found that the lubricating ability of synovial fluid as well as concentrations of lubricin had both significantly decreased at two and three weeks post injury compared to week one. Additionally, Type II collagen peptide concentrations significantly increased at week three, according to the study.

Elastase activity significantly increased at weeks two and three, which significantly correlated with decreasing lubrication at all follow-up points, the authors said. However, concentrations of keratan sulfate epitope 5-D-4 showed no significant changes, they said.

“Loss of boundary-lubricating ability ... after injury is associated with damage to the articular cartilage matrix. This can be attributed to inflammatory processes resulting from the injury, particularly in the early phases,” the authors said.

A retrospective evaluation of synovial fluid aspirated from emergency room patients to alleviate swelling further supports their findings. The researchers found injured patients had greater levels of friction compared to uninjured patients. Injured patients also had increased production of Type II collagen peptides, indicating early cartilage damage, according to a press release.

The researchers found that patients with rheumatoid arthritis had no lubricating ability. This suggests the possible association with cartilage damage is not unique to early stages of a knee injury, “but rather a common feature in inflammatory conditions, both acute and chronic,” the authors said in the study.

“In this study, we were able to quantify loss of lubrication, which has important implications for preventing osteoarthritis,” Jay said in the press release. “If you’re walking on a nonlubricated joint, it’s likely you’ll develop osteoarthritis or induce damage to other areas of the knee,” he added.

For more information:
Elsaid KA, Jay GD, Warman ML, et. al. Association of articular cartilage degradation and loss of boundary-lubricating ability of synovial fluid following injury and inflammatory arthritis. Arthritis Rheum. 2005;52:1746-1755.