What is the best treatment for wrinkles on my knee? (Photo)

A few months ago I noticed that the skin on my left knee wrinkles when I stand up straight. It is only on my left knee and I suspect I have developed it due to often crossing my right leg over the left one when sitting, thus applying constant pressure on my knee. Since I discovered the wrinkles I stopped crossing my legs but the wrinkles are still as bad. I am only 26 years and this seems too early to develope such wrinkles! What would be my best options to reduce/remove this?