Osteoarthritis

Osteo- means “bone”, and -arth- refers to “arthron” which means joint, and -itis means “inflammation”, so osteoarthritis is a disease involving inflammation of the bone and joint cartilage.

It was once thought that the “itis” part of osteoarthritis was a misnomer, and that inflammation didn’t play a role in its development, and that it was mostly a degenerative disease resulting from simple “wear and tear”.

Nowadays, it’s thought that inflammation does indeed play an important role in the development of osteoarthritis.

Alright, so a healthy joint consists of two bones, each with its own layer of articular cartilage, which is a type of connective tissue that allows the two bones to glide against each other essentially without friction.

With Osteoarthritis, we’re really talking about one particular kind of joint which is a synovial joint.

Along with articular cartilage, another important component of synovial joints, and where they get their name from, is the synovium, which along with the surface of the articular cartilage, forms the inner lining of the joint space.

The synovium’s composed of loose connective tissue, blood vessels, lymphatic vessels, and on the surface—”Type A” cells that clear cellular debris and “Type B” cells that produce components of synovial fluid, which helps lubricate the two articular surfaces.

One of the main issues in osteoarthritis is the progressive loss of this articular cartilage, which means there’s not much separating the two bones anymore, which adds a significant amount of friction between them, which then generates inflammation, and triggers pain through the nerve endings in this joint space.

Maintaining healthy articular cartilage is the chondrocyte’s job, a specialized cell responsible for maintaining everything cartilage-related.

The chondrocytes produce and are embedded within a strong gel or extracellular matrix which contains type II collagen, a protein that provides structural support, as well as proteoglycans, which are aggregates of protein and sugar molecules like as hyaluronic acid, chondroitin sulfate, and keratin sulfate.

All of these extracellular components give the cartilage elasticity and high tensile strength, which help weight-bearing joints distribute weight such that the underlying bone absorbs the shock and weight, and these are joints like the knees, hips, and the lower lumbar spine.