The following information may help to address your question:
The exact cause of arthrogryposis multiplex congenita (AMC) is not fully understood. AMC is thought to be related to decreased fetal movement during development, which can occur for a variety of reasons. When a joint is not moved for a period of time, extra connective tissue may grow around it, fixing it in place. Lack of joint movement also means that tendons connected to the joint are not stretched to their normal length, which can make normal joint movement difficult.
In general, there are four causes for decreased fetal movement before birth: