Which of the following conditions indicates muscle atrophy?

Muscle atrophy refers to the wasting or loss of muscle tissue, which can occur due to various underlying conditions. Cachexia is a syndrome characterized by significant weight loss, muscle wasting, and a decrease in overall physical condition, often seen in chronic illnesses such as cancer, AIDS, or heart failure. The presence of cachexia specifically indicates that the body is not only losing fat but also muscle mass, leading to atrophy.

In contrast, hypertrophy refers to the increase in muscle mass and size, usually as a result of exercise or increased workload. Fever is a temporary increase in body temperature often due to infection and does not inherently cause muscle atrophy. Pain may limit movement and activity but does not directly indicate muscle atrophy either. Thus, the correct answer connects directly to a condition known for its association with muscle loss, making cachexia the condition that indicates muscle atrophy.