What Causes Severe Pain From The Left Hip To The Tip Of Toes?

Hi, I've severe pain from my left hip to the tip of my toes. tightness in my knee. cant stretch, cant bend. slight trembling when I get down and climb stairs. Every orthopeodician says nothing wrong with the bone of my knee. I'm continuously taking 1 overon tab for the past 3 months. What's this? not able to go out of home. Which doc is best for this now?