A bone density test is primarily used to diagnose osteoporosis or early bone loss. While it can't directly diagnose arthritis, your doctor may suggest a bone density test if you have inflammatory types of joint diseases like rheumatoid arthritis or psoriatic arthritis, as these conditions can increase the risk of osteoporosis. The test is typically done using dual-energy X-ray absorptiometry (DXA) and measures the density or mass of your bones, helping to assess bone strength. If you have risk factors for osteoporosis or currently have arthritis and are concerned about bone loss, you should talk to your doctor about the possibility of getting a bone density test.