Osteoarthritis and Rheumatoid Arthritis

Arthritis refers to inflammation of a joint, it's one of the most common causes of disability due to joint dysfunction and pain. Osteoarthritis, or OA, is a progressive disorder affecting the synovial joints. Another type of arthritis is rheumatoid arthritis, or RA, which is a chronic autoimmune disorder characterized by inflammation of connective tissue in the synovial joints. Unlike OA, RA is also a systemic disorder, impacting other organs, such as the lungs and blood vessels.

Okay, so one of the main causes of OA are conditions or events that damage the synovial joints, such as repeated wear and tear over time. Having medical conditions, such as obesity and skeletal deformities like congenital hip dislocation can also increase the risk of OA. It’s also more common in people over the age of 50 and those assigned female at birth. On the other hand, RA is likely due to a combination of both environmental and genetic factors that trigger an autoimmune response. RA can occur at any age, though its onset is usually between age 30 to 50; and like OA, its more common in those assigned female at birth.

Now, the main clinical manifestations for both OA and RA are joint pain and stiffness that limit mobility and impact quality of life. In OA, pain typically affects larger weight-bearing joints, such as the knees and hips, and it's usually relieved by rest. Conversely, joint stiffness often develops after periods of rest, and it typically resolves within 30 minutes. Pain associated with RA is usually located in smaller joints, like the hands and feet, and it usually improves with movement.

Patients with OA and RA can also develop joint nodules. In OA, nodules can form in the distal interphalangeal joints, called Heberden nodes, and on the proximal interphalangeal joints, called Bouchard nodes. In patients with RA, firm, subcutaneous rheumatoid nodules develop, usually in bony areas exposed to pressure, like the fingers and elbows; however, nodules can also develop at the base of the spine and back of the head, especially in older patients.

As RA progresses, inflammation can cause deformities of the hands, such as swan-neck deformity, where there’s 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. There’s also metatarsal head dislocation, causing the toes to bend and curl over or under the feet, making walking painful and challenging.

In addition, there are several systemic extraarticular manifestations, such as atherosclerosis, or the build-up of fatty plaques in the arteries; vasculitis, which refers to inflammation of the blood vessels; and pleuritis, or when the tissue surrounding the lungs is inflamed.

Diagnosis of OA and RA starts with the patient’s history and physical assessment. X-Rays, bone scans, and MRIs can provide baseline deformities or be used for monitoring progression of the disease. In both OA and RA, X-ray results will show joint space narrowing. In patients with OA cartilage loss and new bone formation, called osteophytes, can be seen; and in patients with RA, and in patients with RA, early disease findings on X-ray may show soft tissue swelling, bony demineralization with overgrowths, ulnar deviation of the fingers due to the subluxation of the metacarpophalangeal joints, and osteoporosis as the disease progresses.

Blood work will also be drawn to evaluate rheumatoid factor, antinuclear antibodies, anticitrullinated peptide, C-reactive protein, or CRP, and erythrocyte sedimentation rate, or ESR, which will be positive or elevated in patients with RA, but negative in patients with OA.