Occasionally when I have been working with my hands (pruning shears, pulling weeds, even long periods of using mouse or writing) I get a cramp or a tetany in my hand that pulls my hand into a grotesque configuration. Usually my thumb, but sometimes a finger. I cannot move the digit and have to massage my hand and move the digit into a normal position. Could be an age thing (79) as it is more frequent than say 20 years ago. Would like to know cause, how I might prevent and, if it occurs, how i can best mitigate it.