The abnormal breakdown and replacement of bone tissue in Paget's disease may lead to bone deformities such as bowed legs as shown in the picture. Paget's disease may also lead to an enlarged skull or hips or a curved backbone. Deformities are more common in long bones, such as the thigh bone (femur).

A bone affected by Paget's disease can cause complications. For example, if the upper leg bows, it may change how the bones that form the hip joint and knee joint fit together and move, leading to osteoarthritis. Osteoarthritis, in turn, can cause pain and stiffness in the joints and difficulty with walking and other daily activities.