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What Causes It?
Research has shown that anything preventing normal joint movement before birth can result in joint contractures. The joint itself may be normal. However, when the joint is not moved for a period of time, extra connective tissue tends to grow around it, fixing it in position. Lack of joint movement also means that tendons connecting to the joint are not stretched to their normal length; short tendons, in turn, make normal joint movement difficult and contractures may occur.
In general, there are four causes of limitation of joint movement before birth:
- Muscles do not develop properly (atrophy). In most cases, the specific cause for muscular atrophy has not yet been identified. Suspected causes include muscle diseases, for example: congenital muscular dystrophies, maternal fever during pregnancy, and viruses which may damage cells in the spine which transmit nerve impulses to the muscles.
- There is not sufficient room in the uterus for normal movement. For example, the mother may lack the normal amount of amniotic fluid, or have an abnormally shaped uterus.
- Central nervous system and spinal cord are damaged. In these cases, arthrogryposis is usually accompanied by a wide range of other conditions.
- Tendons, bones, joints or joint linings may develop abnormally. For example, tendons may not be connected to the proper place in a joint.
Distinctive skin dimples may be seen over the joints, where the skin appears to be attached to the underlying structures.
*Information in this section is taken from a publication of AVENUES, the arthrogryposis support group in U.S.A.