Congenital myopathies, anterior horn cell disease, and maternal myasthenia gravis have been proposed as causes of the associated amyoplasia. The shoulders generally are adducted and internally rotated, the elbows extended, and the wrists and digits flexed. The hips may be dislocated and usually are slightly flexed. The knees are extended, and the feet are often in the equinovarus position. The leg muscles are usually hypoplastic, and the limbs tend to be tubular and featureless.
Soft tissue webbing sometimes occurs over the ventral aspects of the flexed joints.
The spine may be scoliotic. Apart from slenderness of the long bones, the skeleton is radiographically normal. Physical handicaps may be severe. Intelligence is usually unimpaired or mildly abnormal. Other abnormalities occurring together with arthrogryposis include microcephaly, cleft palate, cryptorchidism, and cardiac and urinary tract anomalies.