Loss of effective joint lubrication in equine synovitis

In a previously healthy joint, uncontrolled inflammation leads to irreversible and progressive damage to the cartilage. Along with these changes comes a progressive lameness. This disease is called degenerative joint disease (DJD). Why does this occur? What can be done to prevent DJD and once it occurs, ameliorate the progression and symptoms?

As our understanding of arthritis grows we are learning that the joint capsule’s inner lining, the synovium, is a key player in arthritis. The synovium is responsible for the production of joint fluid and therefore maintaining a normal joint environment. When inflammation occurs in a joint, say from trauma, the synovium responds with a thinner joint fluid with increased inflammatory mediators. With these changes, there is a loss of lubrication between the two opposing joint surfaces that rub against each other. The inflammatory mediators promote more inflammation.

The below report finds that with acute inflammation in the joint, the ensuing loss of lubrication is much greater than previously thought. Indeed, the loss of lubrication is so great it may be the most critical factor leading to DJD.

For more on the How, Why, and What can be done, see the parent article on this topic: https://horseadvice.com/horse-equine/diseases/lameness-in-horses/joint-bone-ligament-diseases/arthritis-and-djd-an-overview/.
DrO

Loss of effective lubricating viscosity is the primary mechanical marker of joint inflammation in equine synovitis
J Orthop Res. 2024 Jul;42(7):1438-1447. doi: 10.1002/jor.25793. Epub 2024 Jan 30.
Authors
Karan Vishwanath 1 , Erica J Secor 2 , Amanda Watkins 2 , Heidi L Reesink 2 , Lawrence J Bonassar 3 4
Affiliations

1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, USA.
2 Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
3 Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York, USA.
4 Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, USA.

PMID: 38291343
DOI: 10.1002/jor.25793

Abstract

Inflammation of the synovium, known as synovitis, plays an important role in the pathogenesis of osteoarthritis (OA). Synovitis involves the release of a wide variety of pro-inflammatory mediators in synovial fluid (SF) that damage the articular cartilage extracellular matrix and induce death and apoptosis in chondrocytes. The composition of synovial fluid is dramatically altered by inflammation in OA, with changes to both hyaluronic acid and lubricin, the primary lubricating molecules in SF. However, the relationship between key biochemical markers of joint inflammation and mechanical function of SF is not well understood. Here, we demonstrate the application of a novel analytical framework to measure the effective viscosity for SF lubrication of cartilage, which is distinct from conventional rheological viscosity. Notably, in a well-established equine model of synovitis, this effective lubricating viscosity decreased by up to 10,000-fold for synovitis SF compared to a ~4 fold change in conventional viscosity measurements. Further, the effective lubricating viscosity was strongly inversely correlated (r = -0.6 to -0.8) to multiple established biochemical markers of SF inflammation, including white blood cell count, prostaglandin E2 (PGE2), and chemokine ligand (CCLs) concentrations, while conventional measurements of viscosity were poorly correlated to these markers. These findings demonstrate the importance of experimental and analytical approaches to characterize functional lubricating properties of synovial fluid and their relationships to soluble biomarkers to better understand the progression of OA.

Keywords: biomarkers; biomechanics; cartilage; inflammation; osteoarthritis.

© 2024 Orthopaedic Research Society.

• This topic was modified 6 months ago by Robert Oglesby DVM.