If you have knee or ankle problems, what exercise is a good alternative to running?

A huge help for arthritis or any degenerative joint disease is to focus on strengthening the muscles that are around that joint. For example, if you have arthritis in your knees, you want to strengthen the quads, hamstrings, calves and all those surrounding muscles of that joint. This way the muscles will take the force instead of the joints. Any type of low-impact exercising like lifting weights or water aerobics are good alternatives to running. It would also be helpful to get the help of a professional, such as a doctor, physical therapist or personal trainer.