I painted this one for my friend Dania, she had this condition. Frozen shoulder is known as adhesive capsulitis, and is associated with significant amounts of pain and loss of ability to move the shoulder. The cause is rally unknown, but occurs more frequently as we get older (40-70 years old), and women. So it is worse to be an older women when it comes to muscle and joint pain problems. The most effective treatment is a steroid injection into the joint, but people often undergo physical therapy to improve their motion and further reduce the pain.
The painting is the shoulder joint seen through an arthroscope often used for surgical repair of shoulder injuries. It shows the ligaments and capsule surrounding the joint. The injured and painful area is pink/red while the more normal areas are closer to white.