1) Weight reduction
Extra weight is bad for the joints, as it increases the load on them, and has damaging effect leading osteoarthritis.
2) Proper exercises, those which do not harm the joints
These include low-impact and non weight bearing exercises like cycling and swimming. Yoga, Pilates and slow to moderate speed walking are okay, if these are not stressful. While walking, wear comfortable shoes and try to walk on non-concrete surfaces that are not uneven.
3) Watch your bio mechanics in activities of daily living
Avoid undue stress on the joints. Maintaining a proper mechanics minimizes strain on the joints, it may otherwise manifest later as osteoarthritis (OA).
4) Prevention and treatment of injuries
Too many sprains and joint injuries, or insufficient treatment of these, can lead to arthritis. Hence early attention and proper treatment of these injuries by a specialist is must.
5) Taking supplements is also potentially useful
Vitamin D and various nutritional supplements (Nutraceuticals) like Curcumin extract, Collagen peptides, Rose hip extract, Ginger, and Green tea have shown to help cartilage avoid deterioration.