How is hitch hikers thumb determined?

Hitchhiker's thumb, or distal hyperextensibility, is primarily determined by genetics and is associated with the flexibility of the thumb joint. It occurs when the thumb can bend backward at the last joint beyond the normal range of motion. This trait is often inherited as a dominant genetic characteristic, meaning that it can be passed from one generation to the next. The underlying mechanism involves variations in the connective tissues that affect joint stability and flexibility.