<s>[INST] What Causes Arthritis Pain? Why Is It So Variable? [/INST] The pain of arthritis may come from different sources. These may include inflammation of the synovial membrane (tissue that lines the joints), the tendons, or the ligaments; muscle strain; and fatigue. A combination of these factors contributes to the intensity of the pain.

The pain of arthritis varies greatly from person to person, for reasons that doctors do not yet understand completely. Factors that contribute to the pain include swelling within the joint, the amount of heat or redness present, or damage that has occurred within the joint. In addition, activities affect pain differently so that some patients note pain in their joints after first getting out of bed in the morning, whereas others develop pain after prolonged use of the joint. Each individual has a different threshold and tolerance for pain, often affected by both physical and emotional factors. These can include depression, anxiety, and even hypersensitivity at the affected sites due to inflammation and tissue injury. This increased sensitivity appears to affect the amount of pain perceived by the individual. Social support networks can make an important contribution to pain management. Source: NIAMS. Link: https://webharvest.gov/peth04/20041015190953/http://www.niams.nih.gov/hi/topics/arthritis/arthpain.htm. Field: Rheumatology. Disease: Arthritis </s>