Stretching as much as possible. With HSP, most cases, your legs will stay tightened up and periodical stretching helps to relieve some of the associated discomfort.
Baclofen. Most are 50-50 on whether to have the spinal pump or take it in pill form. It is a muscle relaxer but after time goes by, it has in my case only taken the edge off the cramping and has not completely relieved of it.