Which condition is characterized by painful inflammation and stiffness of the joints?

Arthritis is characterized by inflammation and pain in the joints, leading to stiffness and reduced mobility. This condition can occur in various forms, such as osteoarthritis, which is associated with wear and tear of the cartilage, and rheumatoid arthritis, an autoimmune disorder that affects the joints. The inflammation involved in arthritis can cause significant discomfort and hinder daily activities due to the stiffness that typically occurs as the joint is used.

In contrast, osteoporosis involves the weakening of bones and does not primarily affect joint inflammation. Fibromyalgia presents with widespread musculoskeletal pain, fatigue, and tender points but is not limited to joint-related issues. Tendinitis refers to the inflammation of a tendon, which connects muscle to bone, and while it can also be painful and involve stiffness, it does not encompass the broader joint inflammation typical of arthritis. Thus, arthritis is the most accurate choice for describing a condition defined by painful inflammation and stiffness specifically within the joints.