Which chronic disorder is noted for widespread muscle pain, tenderness, and fatigue?

Fibromyalgia is characterized by widespread muscle pain, tenderness, and fatigue. This condition affects the way the brain processes pain signals and can lead to a heightened sense of pain throughout the body. Individuals with fibromyalgia often experience additional symptoms such as sleep disturbances, cognitive difficulties, and emotional issues, which contribute to their overall discomfort and fatigue.

In contrast, rheumatoid arthritis primarily involves joint inflammation and is marked by painful swelling, particularly in the hands and feet, but does not typically present with the widespread muscle pain that defines fibromyalgia. Osteoarthritis is a degenerative joint disease that focuses on the breakdown of cartilage in the joints, leading to localized pain and stiffness rather than systemic muscle pain. Lupus, an autoimmune disorder, can cause a variety of symptoms including joint pain and fatigue, but it is generally more complex and not defined solely by widespread muscle pain.

Thus, the defining characteristics of widespread muscle pain, tenderness, and fatigue distinctly align with fibromyalgia, making it the correct answer.