5 cm)Peripheral joints for e.g. shoulders and hips (root joints) are also involved in l/3rd patients.Extraarticular manifestations like acute anterior uveitis (in 5%); rarely aortic valve disease, carditis, and pulmonary fibrosis.Pathological changes proceed in three stages-Inflammation with granulation tissue formation and erosion of adjacent bone.Fibrosis of granulation tissueOssification of the fibrous tissue, leading to ankylosis of the joint.Clinical featuresThe low back pain of insidious onsetDuration usually less than 3 monthsSignificant morning stiffness and improvement with exerciseLimited chest expansionDiffuse tenderness over the spine and sacroiliac jointsLoss of lumbar lordosis increased thoracic kyphosisDecreased spinal movements (especially extension) in all directions.Radiological featuresCardinal and earliest sign is erosion and fuzziness of the sacroiliac jointsSquaring of vertebral bodiesSyndesmophytes (described earlier) giving the appearance of a "bamboo spine".Other investigationsESR and CRP are usually elevatedHLA-B27 is present in 95% of cases.TreatmentGeneral measures to maintain satisfactory posture and preserve movement.NSAIDsTNF inhibitors for severe diseaseOperations to correct deformities ComplicationsSpinal fracturesHyperkyphosisSpinal cord compressionLumbosacral nerve root compression">