It happens to me, I have hereditary motor sensory neuropathy, peripheral.
I dont know why, it is getting worse with the years.
As far as I see, it that is not very far, there is 2 explanations:
1. Muscle fibers are out of control, usually doing nothing but might contract by their own idea.
2.Muscle fibers on one side of the joint slacking, and those on the other side have no counterforce and pulls too hard.
Anyhow I do as you: Try to force the joint back to normal and shake off cramps.
good luck, companion
Per, Norway