Medically reviewed by Scott Zashin, MD Rheumatoid arthritis (RA) is known for causing all-over inflammation and pain. It happens when the immune system malfunctions and attacks the synovium, the ...

Explores the anatomy and functions of human joints ... the ball-and-socket joint of the shoulder and hip, and the complex structure of the knee. The film describes the movements allowed by ...

Ball and socket joints also allow flexion and extension. Flexion of the shoulder joint occurs when the humerus (upper arm) moves forwards from the rest of the body, which happens at the end of an ...