system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what causes the stereotypical bent hand and arm position that many mentally handicapped people display?
gpt
Contractures happen when people lose control of their muscles and stop using them. Over time, the muscle atrophies and shortens, pulling the limb into a contracted position. This can be mitigated through physical therapy, but unfortunately people with severe disabilities often don't recieve it. This is both because PT time is a limited resource best spent on people who have a hope of recovery, and because the mentally retarded often don't have anyone advocating for their needs.

This is not only seen on people with mental disabilities. It happens frequently to bed-bound quadraplegics, particularly when the cause of their illness is a spinal injury. All the muscles still work just fine in such patients, but their brain can't tell them to do anything and they atropy. This often results in perfectly lucid people with severely contracted limbs. Fortunately, such patients are capable of advocating for themselves and are thus more likely to have physical therapy, but it isn't guaranteed.