In old age, people often suffer from stiff and inflamed joints. What is this condition called? What are the possible reasons for these symptoms?

(N/A) The condition characterized by stiff and inflamed joints is known as $Arthritis$.
$Arthritis$ is an inflammation of the joints that causes pain, swelling, and stiffness.
Possible reasons for these symptoms include:
$1$. Aging: Wear and tear of the articular cartilage over time.
$2$. Autoimmune reactions: The immune system attacks the joint tissues (e.g., $Rheumatoid arthritis$).
$3$. Metabolic factors: Accumulation of uric acid crystals (e.g., $Gout$).
$4$. Infection: Bacterial or viral infections affecting the synovial fluid.