Arthrogryposis is a birth defect that describes a wide variety of joint disorders. The joints can be fused, deformed or stiff. This occurs in approximately 1 in every 3,000 live births (which is very rare). Many different factors or conditions can cause Arthrogryposis. Anytime a fetus is unable to move freely in the womb, Arthrogryposis can occur. This can be due to cramped quarters (as occurs with multiple births), low levels of amniotic fluid or a misshapen uterus.