Winny will make you lose the watery substance or synovial fluid in your joints while your on.. I would definately suggest that you not use it more than 4 wks straight if your worried about joints.
Also, if you go longer like 8 weeks or if you actually want to feel a difference you need to stack it. I imagine that you get tested so, you should stack it with test prop, which will be in your system a little bit less than winny tabs. Tabs are dectable for 4wks.. injectables are dectable for 8wks after use.
Good luck... and if you stack it with test you'll be fine... and get much stronger...