To better understand adult still's disease, it helps to understand the anatomy of the joints.

The bones in all joints have a smooth lining called articular cartilage. Cartilage provides a gliding surface to help joints move. All joints are lubricated with a slippery liquid known as synovial fluid.

Joint cartilage may break down due to inflammation, overuse or injury. This can result in the bones of a joint making contact. This in turn causes abnormal bone growth, more inflammation, pain and stiffness.

Anatomy of joints commonly affected by osteoarthritis:

• Cervical spine
• Knee
• Lumbar spine
• Hip
• Wrist and hand
• Hand joints affected by osteoarthritis