What is the medical term meaning within a joint?

Arthralgia is the medical term for joint pain. Arth=joint... -algia=pain

Joint inflammation is Arthritis.

-itis=inflammation
There are many causes of joint pain, and in order to find joint pain remedies, you need to find the cause of your pain. Joint pain can in general be divided into a few separate categories, or causes in general. Sometimes it may be a combination of more than one
Arthralgia is a general term for any joint pain.
Arthralgia is pain in a joint. Arth- means joint, -algia is pain.

Polyarthralgia can be used to describe pain in multiple joints (usually used when there is pain in five or more joints.) Poly- means many.

Related terms:

Arthritis means pain from inflammation, which could be caused by a disease, disorder, injury, or infection of the joint.

Polyarthritis means pain from inflammation of multiple joints.
arthralgia
Arthritis