Rheumatoid arthritis and osteoarthritis: Pathology review

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Rheumatoid arthritis and osteoarthritis: Pathology review



Rheumatoid arthritis and osteoarthritis: Pathology review

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A 65-year-old man comes to his primary care provider for evaluation of pain in both knees. His symptoms worsen with activity and improve with rest and ibuprofen. The patient had previously been an avid runner but had to stop due to the joint pain. Past medical history is notable for hypertension and a right fibular fracture, which occurred after a biking accident. Vitals are within normal limits. Examination of the affected joints reveals crepitus and mildly reduced range of motion. The remainder of the patient’s physical examination is noncontributory. Knee imaging is ordered, and the results are as follows:

Reproduced from: Radiopedia

Which of the following additional findings, if present, would best support the patient’s diagnosis?


Jody is a 55 year old woman who presents with a 6 month history of bilateral hand and wrist stiffness.

She mentions that the stiffness lasts for more than an hour a day but tends to improve as she uses the affected joints.

Examination shows swelling, limited range of movement, and subcutaneous nodules over the proximal interphalangeal joints, but no redness.

Then you see Kerry, a 60 year old woman who comes in with a 1 year history of pain in the right knee that has gotten progressively worse.

The pain is worse in the evening or with use of the affected limb and is associated with stiffness, which typically occurs at rest and lasts around 10 to 15 minutes.

Examination reveals Kerry is obese, has bowing of the right knee, and that the affected joint has a limited range of motion.

Blood tests are ordered in both cases, showing in Jody’s case high levels of rheumatoid factor (RF) and anti-citrullinated peptide antibody (ACPA), whereas in Kerry’s case both antibodies were absent.

Both people have arthritis.

Now, a healthy joint usually consists of two bones, each with its own layer of articular cartilage.

Articular cartilage is a type of connective tissue with a lubricated surface that acts like a protective cushion for bones to smoothly glide against.

Now, there are many types of joints, including fibrous, cartilaginous, and synovial joints, which have additional components depending on their function.

For example, synovial joints, like those of the wrist, elbow, knees, shoulders, and hips, are mobile joints that connect two bones via a fibrous capsule that is continuous with the periosteum, which is the outer layer of bones.

The fibrous capsule is lined with a synovial membrane that has cells that remove debris and produce synovial fluid, which is a viscous fluid found inside the joint capsule to lubricate the joint.

Together, the synovial membrane and articular cartilage form the inner lining of the joint space.

Now, arthritis refers to a group of diseases that cause destruction of one or more joints, and it can be classified as inflammatory or non-inflammatory.


Rheumatoid arthritis (RA) and osteoarthritis (OA) are both types of arthritis, but they have different causes and characteristics.

Rheumatoid arthritis is an autoimmune inflammatory disease that causes progressive and symmetric destruction of at least three joints, especially the proximal interphalangeal joints, which leads to morning stiffness that lasts for more than an hour and improves with use. It can also present with extra-articular symptoms like uveitis, pulmonary fibrosis, and rheumatoid nodules. The treatment of rheumatoid arthritis involves non-biological and biological DMARDs, nonsteroidal anti-inflammatory drugs (NSAIDs), and glucocorticoids.

Osteoarthritis, on the other hand, is a chronic condition characterized by the breakdown of joint cartilage and underlying bone followed by inadequate repair. Now, unlike rheumatoid arthritis, which is an autoimmune disorder, osteoarthritis is considered a mechanical degenerative joint disorder. This is because the main culprit seems to be the daily stress applied to joints in our lifetime, especially to weight-bearing joints like those of the ankle, knee, and hip. Symptoms of OA include joint pain, stiffness, and decreased range of motion. Treatment of OA involves losing weight, physical therapy, and pain management with drugs like acetaminophen and NSAIDs.


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