Osteoarthritis and Rheumatoid Arthritis

Question 1

What is Osteoarthritis?

Answer 1

condition characterised by the progressive loss of articular cartilage and remodelling of the underlying bone – “Wear and tear” and repair! (TeachMeSurgery, 2019)

A common arthropathy occurring in 15% of adults >55 years of age, and 80% of those over 75

Most commonly affects the joints of the hands, feet, hips and knees

Question 2

Pathophysiology of OA

Answer 2

Degradation of cartilage and remodelling of bone due to an active response of chondrocytes in the articular cartilage and the inflammatory cells in the surrounding tissues

Release of enzymes from these cells breaks down collagen and proteoglycans (proteins found in connective tissue) which destroys the articular cartilage

Exposure of the underlying subchondral bone leads to sclerosis, followed by reactive remodelling changes that lead to osteophyte formation and bone cysts

Decreases the capability of the joint to absorb impact

Question 3

Signs and Symptoms of OA

Answer 3

Signs
Localised swelling/joint effusions – asymmetrical (doesn’t always affect same joint on both sides)
Crepitus
Muscle wastage
Malalignment of joint
Deformity of joints
Reduced range of movement (ROM)

Symptoms
Chronic and gradually worsening
Pain and stiffness in the joints
Relief from symptoms upon rest

Question 4

Risk factors of OA

Answer 4

Age
Obesity
Repetitive strain injuries
Previous traumatic injuries
Gender (most common in older females)

Question 5

Radiological Features of OA

Answer 5

Loss of joint space

Osteophytes

Subchondral cysts (caused by increased articular pressure from the area of absent cartilage being transmitted to the bone marrow, resulting in a fluid filled cyst)

Subchondral sclerosis (to strengthen the bony trabeculation)

Question 6

What is Rheumatoid Arthritis?

Answer 6

A chronic systemic autoimmune disease that primarily affects the joints

Disease 2-3 times more likely in females

Onset in adulthood c. 40-50 years of age

Affects between 0.5-1% of population

Question 7

Pathophysiology of RA

Answer 7

Exact cause unknown

Genetic predisposition HLA-DR B1 plus an environmental trigger cause autoimmune response which attacks synovial structures

Synovial membrane becomes hyperplastic (increased amount of tissue resulting from cell proliferation) – causing an increase from 2 to 10 cell layers thick

This layer becomes infiltrated with macrophages, B & T lymphocytes (white blood cells)

Question 8

Progression of RA

Answer 8

Synovial changes are apparent due to the migration of the synovial membrane into surrounding areas (pannus formation)

The synovial membrane secretes cytokines and enzymes which destroy cartilage and bone

Effects are also seen in tendons and bursae around joints

Question 9

Signs and Symptoms of RA

Answer 9

Signs
Swollen joints in the same joint on both sides of the body – symmetry
Growth of firm round nodules on joints

Symptoms
Pain and stiffness in joints
Reduced range of joint movement
Fatigue and muscle weakness
Loss of appetite with associated weight loss

Question 10

Radiological Features of RA

Answer 10

Soft tissue swelling

Osteoporosis particularly around the joint initially and then more generally

Symmetrical joint space narrowing

Marginal erosions due to pannus formation

Ulnar deviation of digits

Question 11

Image differences of OA and RA

Answer 11

OA
Subchondral Cysts
Osteophyte formation
Joint space narrowing
Sclerosis

RA
Juxta-articular osteoporosis
Ulnar deviation of digits
Erosions at the synovial insertions