I would want more information. How active? How advanced is the arthritis and osteoporosis? Is the client over weight? What is the status of the major joints? (Knees? Ankles? Wrists? Shoulders? Are the hips just arthritic or is that that site of bone loss? You say active, how active? Vigorously exercises or moderately or lightly? Do you have clearnace for exercise? If not, get it. And get recommendations on how heavy for weight bearing exercises and let the physician know what you have in mind from your screenings and interview with the client. IF the client is not used to exercise. I recommend starting low intensity and low weight bearing. Improve overall fitness first. LIke cardio and mobiility/stability. Aquatic exercise isn’t great for osteoporosis, but it is awesome for arthritis. Especially in a warm water pool/therapy pool (85 -90 degrees). Is the client on medication for either issue? What are the possible interactions with exercise? I would definitely want clearance for any type of plyometrics. No matter how low intensity. Walking is usually pretty helpful. And progressing to weighted walking can be very effective in stimulating bone density. But progress carefully. And of course, with physician clearance. How are the clients feet? A lot of clients in that age range have foot issues from wearing stylish but unkind footwear for years. So, make sure her shoes are high quality for the exercise you choose. These are things I would start off figuring out.