Normal Joint: In a normal joint (where two bones come together), the muscle, bursa and tendon support the bone and aid movement. The synovial membrane (an inner lining) releases a slippery fluid into the joint space. Cartilage covers the bone ends, absorbing shocks and keeping the bones from rubbing together when the joint moves.
Osteoarthritis: In osteoarthritis, cartilage breaks down and the bones rub together. The joint then loses shape and alignment. Bone ends thicken, forming spurs (bony growths). Bits of cartilage or bone float in the joint space.
Rheumatoid Arthritis: In rheumatoid arthritis, inflammation accompanies thickening of the synovial membrane or joint lining, causing the whole joint to look swollen due to swelling in the joint capsule. The inflamed joint lining enters and damages bone and cartilage, and inflammatory cells release an enzyme that gradually
digests bone and cartilage. Space between joints diminishes, and the joint loses shape and alignment.