Oy I know the feeling...I hit 40 and six months later I feel 20 years older! I've had arthritis in my shoulders for years. Sprained my ankle ten years ago and it still bothers me too. Got run over by a bike messenger! Swimming has helped alot for me. Non-impact sports seem to be the answer. Bike riding and horse back has also been great. Strengthens upper legs without hurting below the knee.
Hope you feel better.
Claudia