I started jumping rope 4 to 5 times a week last August. I made the mistake of moving to the concrete side walk when the soil I had been using started getting soggy(the end of September). Last October I started having pain in both knees. The hard surface (that I was dumb enough to jump on) I decided was what pushed my knees over the edge so I stopped jumping rope and about a week later they started feeling better(as in it didn't hurt to get out of a chair every time I sat down). Edit:However, I am still haveing problems with them.
I have never had particularly good knees but I had not previously had any trouble with them. Some days are better than others. Sometimes I have pain in only one knee. I have not been able to isolate any particular activities that aggravate them or help them. I want to continue training my legs but I am not sure what exercised to do.
I have been looked into supplements like glucosamine, chondroitin , msn etc and I have not read much of anything that convinces me that they are worth spending money on. I have also been taking fish oil several times a day and I have not noticed much improvements.