The rheumatologist is the doctor who specializes in the diagnosis and treatment of diseases that affect the joints, muscles, tendons and bones.
The orthopedist is a doctor who specializes in the skeletal muscle system of the human body including bones, joints, ligaments, tendons, muscles and nerves.
A physiatrist is a doctor who specializes in diseases that affect the brain, spinal cord, nerves, bones, joints, ligaments, muscles and tendons and is responsible for restoring lost abilities due to illness or injury.