Surprisingly, some people just don't have pain with osteoarthritis even with cartilage loss. Patients with painful OA usually have other symptoms such as swelling, breakdown of bone underneath the cartilage, and tendinitis or bursitis.

It's not clear why some people have painful symptoms and others don't. Clearly the majority of patients do have pain and other problems. In fact if scientists could find out why patients like you don't have pain the information might be able to help others.

Pain is less likely when only the cartilage is affected since cartilage doesn't have pain fibers. Damage to the underlying bone that does have many pain fibers can lead to severe pain. Some joints with OA seem less likely to be painful. For example hip OA is more likely to cause symptoms than OA in the hand.

Finally, the difference in patient-response to OA may be genetically linked. It's uncertain what those genetic factors may be.

Reference:

David T. Felson, MD, MPH. Risk Factors for Osteoarthritis. In Clinical Orthopaedics and Related Research. October 2004. Vol. 427S. Pp. S16-S21.'