Do the radiological changes of classic ankylosing spondylitis differ from the changes found in the spondylitis associated with inflammatory bowel disease, psoriasis, and reactive arthritis?
Some of the radiological differences described by McEwen et al, notably the asymmetry, the less severe changes, and the distinctive syndesmophytes in psoriasis, have been confirmed. A number of phypotheses are proposed to explain these differences including biomechanical, biochemical, and genetic factors.
Premorbid knees do not have diffuse cartilage thinness. Rather the cartilage is normal or thicker with denuded areas suggesting that this may be the initial pathology rather than diffuse thinning.