What is the medical term for inflammation of the joints?

"Arthritis" literally means joint inflammation. Joints are places where two bones meet, such as your elbow or knee. There are many different types of arthritis with different causes and treatments. In some types, other organs, such as your eyes, heart, or skin, can also be affected. Common symptoms of arthritis include pain, redness, heat, and swelling in your joints. If you have arthritis, it is important for your doctor to diagnose the type of arthritis you have so that you can get the proper treatment. Fortunately, current treatments allow most people with arthritis to lead active and productive lives.

Source: NIH