Arthritis is when joints are painful, red, hot, swollen. Arthralgia means that joints simply hurt. The same diseases can cause both. But often “joint” pains may not involve joints at all, but be due to tendons, ligaments, bursa, bones, or muscles. That’s a different topic (Musculoskeletal Conditions).
Some diseases affect many joints, usually small ones like wrists, hands, fingers; ankles, feet, toes. This gets called Polyarticular (“articular” = “joint”).
Other diseases affect only one joint (Monoarticular), or a just few (Oligoarticular). These are usually the larger joints, like shoulder, elbow, maybe wrist; hip, knee, maybe ankle.
Select a topic on diagnosing Joint Diseases (arthritis / arthralgias):
Many Joints (Polyarticular)
Few Joints / Just One Joint (Oligoarticular / Monoarticular)