Osteoarthritis

Note: Charcot joint is an extreme form of osteoarthritis seen in patients with neurological dysfunction in which there is rapidly destructive osteoarthritis, the production of loose bodies, severe subluxation and even dislocation of the joint.

Morphology: changes manifest morphologically as alterations in cartilage, synovium and bone…

1. Earliest changes are loss of proteoglycans and decreased metachromasia of the articular cartilage, associated with focal loss of chondrocytes alternating with areas of chondrocyte proliferation (cloning) and increased matrix basophilia.

2. Next, fissuring, pitting, and flaking of the cartilage develop, followed by vertical clefts down to the subchondral bone.

3. Flaking of the cartilage exposes underlying bone, which appears ivory-like (eburnation) as continued joint motion polishes the surface.

4. Subchondral microcysts and fractures may develop.

5. Synovium shows a mild chronic inflammatory infiltrate (non-specific synovitis) can develop osteocartilaginous metaplasia, fragments of which create osteocartilaginous loose bodies (joint mice) within the joint space.

Overview: changes in general forms of arthritis

Cartilage:

• Clefting/splitting

• Cloning repair and metaplasia

• Loss of matrix basophilia

• Cartilage necrosis (uncommon)

Synovium:

• Varying degrees of hyperplasia and hypertrophy

• Hemosiderin deposition

• Reaction to joint wear / breakdown products

• Presence of loose bodies

Bone:

• Superficial areas of subchondral necrosis

• Reactive sclerosis and cystic change

• Microfractures

• Formation of osteophytes

Synovial fluid:

• Infiltrates (inflammatory or otherwise)

• Pathogens

• Various substances and crystals

Category: Orthopedics Notes , Pathology Notes