Phenylbutazone used to be standard therapy for spondylitis, but is rarely used because of a small risk of marrow aplasia. Nevertheless, it almost certainly outperforms other NSAI and is worth considering. Occasionally, surgery is required to correct kyphosis - usually a low lumbar osteotomy, introducing a compensatory lordosis. Radiotherapy was widely used in the 1960s but increases the risk of malignancy. It may be suitable for highly selected cases using modern selective planning techniques, but is not generally recommended.
Erosions tend to start at ligament insertions rather than cartilage margins.
Arthritis of a few medium sized or large joints, such as knee and wrist is also common, but is not specific to psoriasis. HLA-Cw6 is associated with psoriasis but not specifically with joint disease. I suggests that psoriatic arthropathy relates to altered inflammatory cell activation thresholds as in ankylosing spondylitis. However, a range of alternative genetic factors appear to contribute to the different patterns of disease. The value of slow acting antirheumatic drugs in psoriatic arthropathy is uncertain.