What Causes Recurring Numbness On My Thigh?

I have started getting a numb feeling on the outside of one thigh (about 4 inches square) which lasts for about 10 minutes. It doesn't hurt, but just feels dead. I did hurt that same patch 10 years ago when I went skiing and had a massive bruise there for months. But I have only just started getting the numbness. Any thoughts on the matter??? Thanks.