In which of the following arthritis erosions are not seen:

Ans. is b' i.e., Systemic lupus erythematosus (SLE) About Musculoskeletal manifestation in SLE patients, Harrison writes -"Poly arthralgias and polyarthritis eventually occur in 90% of SLE patients.The arthritis initially involve the small joints in hands, knees and wrists.Joint deformities develop in only 10%.Erosions on joint X-rays are rare, their presence suggest a non lupus inflammatory arthropathy such as rheumatoid arthritis."Joint erosion are well known in all the other three options.