Arthritis - Osteoarthritis and Rheumatoid Arthritis

Osteoarthritis or oa and rheumatoid arthritis or ra are diseases that affect the synovial joints. Osteoarthritis is mostly a degenerative disease.

While rheumatoid arthritis is a systemic autoimmune disease that can also impact other organs like the heart and lungs. Joints or the places where bones meet can be classified into three main groups based on their structure and range of movement.

Fibrous joints like those between the bones of the skull and young Children are composed of a thin layer of fibrous tissue that allows for some movement to accommodate a child's growing brain.

By adulthood. The fibrous tissue is replaced by bone.

On the other hand, cartilaginous joints like the joints of the spine contain a pad of fibrocartilage allowing for some movement.

Lastly, synovial or diarthrodial joints like those of the wrist, shoulders, hips and knees are freely movable. Ok.

Let's take a closer look at synovial joints which consist of two bones, each with its own layer of articular cartilage. A type of connective tissue that provides cushioning and allows the bones to glide against each other without friction.

The cartilage has high tensile strength which helps weight bearing joints like the knees to distribute weight So the underlying bone absorbs the shock and weight.

An important component of the articular cartilage are special cells called chondrocytes, which are essential for the maintenance and repair of the cartilage surrounding the joint is an outer fibrous joint capsule that forms an inner space called the joint cavity, which is filled with synovial fluid.

The inner surface of the joint capsule is lined with a synovial membrane or synovium, which is mostly composed of connective tissue, elastic fibers, blood and lymphatic vessels.

It also contains macrophages that remove bacteria and debris and fibroblasts that produce a viscous substance called hyaluronate, which is the main component of the synovial fluid that lubricates the articular surfaces.

Now, osteoarthritis is caused by damage to the synovial joints and can be categorized as primary or secondary, primary or idiopathic osteoarthritis occurs due to risk factors such as being biologically female, advanced age, obesity, joint trauma and occupations that involve heavy lifting, prolonged standing or repetitive motion.

In contrast, secondary osteoarthritis occurs when there is a preexisting joint abnormality that can initiate biomechanical stress on the joint like Marfan syndrome.

On the other hand, the exact cause of rheumatoid arthritis is unknown though it likely involves genetic epigenetic and environmental factors that give rise to an autoimmune response triggers thought to initiate this response include environmental agents like exposure to cigarette smoke and certain bacteria or viruses.

Additionally, individuals with mutations in genes that play a role in the immune system like the HLA DRB, one gene are at an increased risk of rheumatoid arthritis and like osteoarthritis.

Biological females are more likely to develop rheumatoid arthritis and risk increases with age. Ok.

So, osteoarthritis occurs due to degradation, inadequate repair and loss of articular cartilage, chondrocytes that usually repair, injured, articular cartilage lose their ability to function.

This leads to a gradual degradation of the articular cartilage over time, which means eventually there's not much cartilage separating the two bones anymore.

So now there's a significant amount of friction between them. As the cartilage deteriorates, cracks and pits develop along with osteophyte formation, which are bony growths on the articular surface.

As a result, chronic low level inflammation is generated which contributes to the progression of the disease. On the flip side.

The autoimmunity process of rheumatoid arthritis is mediated by autoantibodies against self antigens and activation of immune cells within the joints.

Immune cells release inflammatory mediators that cause inflammation and tissue injury. The inflammation eventually creates a panis which is a thickened synovial membrane consisting of inflammatory cells and granulation tissue.

This damages the articular cartilage, joint capsule and bone as well as the surrounding ligaments and tendons resulting in joint deformity and impaired function.

Unfortunately, the cytokines released by the immune system don't just stay in the joints. Instead, they can cause extra articular symptoms in various organ systems all over the body.

Now, both osteoarthritis and rheumatoid arthritis can cause joint pain, stiffness, limited range of motion and impaired mobility.

But in different ways in osteoarthritis, deep achy joint pain typically manifests in large weight bearing joints like the knees and hips.

Pain tends to increase with activity and resolve with rest. Whereas stiffness can occur after resting and resolves with activity.

Also, osteoarthritis is often asymmetric, meaning its localized to one joint on one side of the body. Though it can affect more than one joint.

In contrast, rheumatoid arthritis affects smaller joints like the metacarpophalangeal and interphalangeal joints of the fingers and the metatarsophalangeal joints of the toes.

And unlike osteoarthritis, the pain usually improves with activity. The pain associated with rheumatoid arthritis tends to be symmetric meaning it affects the same joint groups on both sides of the body.

Other manifestations of osteoarthritis include joint effusion which is inflammation and swelling around the joint crepitus or a grating sensation caused by bone on bone friction may also occur related muscle weakness can accentuate joint.

Instability causes a feeling of buckling or giving way and can impair balance. Increasing the risk of falls with rheumatoid arthritis, constitutional symptoms of inflammation like generalized stiffness, aches, fatigue and weight loss are often present early on.

As rheumatoid arthritis progresses, inflammation can cause pain and deformities of the hands such as ulnar deviation where the metacarpophalangeal joints bend toward the ulna swan neck deformity where there is hyperextension of the proximal interphalangeal joint along with flexion of the distal interphalangeal joint.

So the finger resembles a Swan's neck and boutonniere deformity where the proximal interphalangeal joint is flexed along with hyperextension of the distal interphalangeal joint which makes the knuckle look like.

It's being pushed through a buttonhole, both osteoarthritis and rheumatoid arthritis can also lead to the development of unusual growths in osteoarthritis.

Bony growths can form in the distal interphalangeal joints called Heberden nodes and on the proximal interphalangeal joints called Bouchard nodes with rheumatoid arthritis, tissue growths form firm subcutaneous rheumatoid nodules usually in bony areas exposed to pressure, like the back of the fingers and elbows.

These nodules can also develop within the heart and blood vessels causing pericarditis and arterial occlusion and in the lungs, they can lead to diffuse pleuritis as a quick recap, osteoarthritis and rheumatoid arthritis are diseases that affect the synovial joints.

Osteoarthritis is mostly a degenerative disease. While rheumatoid arthritis is a systemic autoimmune disease that can also impact other organs like the heart and lungs.

Some of the main clinical manifestations of both osteoarthritis and rheumatoid arthritis are joint pain, stiffness, limited range of motion and impaired mobility.