If you haven’t already, check with your health care provider about any specific exercise recommendations or limitations related to your arthritis; depending on the nature of your pain, a physical therapy evaluation and/or treatment may be recommended prior to beginning strength training.
A balanced strength training program targets all major muscle groups — chest, back, shoulders, arms, core, hips, upper and lower legs. General leg-strengthening exercises such as standing leg extensions, prone hamstring curls, and calf raises will help prepare your leg muscles to bear more of the load when you move from a seated to standing position. You could also perform stability ball wall squats within a pain-free range of motion to strengthen hips and legs.
Keep in mind that when you’re living with a chronic condition like arthritis, you need a fitness plan tailored to your specific needs. Your best bet is to work with a certified fitness professional experienced in designing exercise programs for people with musculoskeletal issues.