Arthrogryposis multiplex congenita (AMC): A disorder that develops before birth (prenatal), is present at birth (congenital), and is characterized by reduced mobility of many (multiple) joints.

In AMC the range of motion of the joints in the arms and legs is usually limited or fixed. Joints affected may include the shoulders, elbows, wrists and fingers and the hips, knees, ankles, and feet -- virtually any and all joints.

The impairment of joint mobility is often accompanied by overgrowth (proliferation) of fibrous tissue in the joints (fibrous ankylosis).

AMC was once thought to be a single disease. It is clearly many. The mechanisms responsible for AMC are presumed to be the same as for all arthrogryposis, irrespective of the number of joints involved:

• Neurologic deficits
• Muscle defects
• Connective tissue and skeletal defects
• Fetal crowding or fetal constraint
• Maternal neuromuscular diseases -- myotonic dystrophy and myasthenia gravis.

Arthrogryposis means crooking of the joint. It comes from the Greek "arthro-", joint + "gryposis ", crooking.