Revised final table of contents: 1.Introduction. 2.Epidemiology of Piriformis Syndrome. 3.Predisposing Factors. 4.Aetiology of Piriformis Syndrome. 5.Specific tests for the PS 6.Pathophysiology 7.Differential Diagnosis 8.Imaging 9.Electro-diagnostic studies 10.Intrapelvic Causes of Sciatica in Piriformis Syndrome 11.Pyomyositis of the Piriformis Muscle 12.Bipartitite Piriformis giving rise to sciatic nerve entrapment 13.Hydrodissection of Piriformis Syndrome 14.Composite Anatomical Variations between the Sciatic Nerve and the Piriformis Muscle 15.Epidemiology.Clinical Diagnosis of Piriformis Syndrome 16. Peroneal Neuropathy in Piriformis Syndrome 17. Physiotherapy for Piriformis syndrome 18.Treatment of Piriformis Syndrome 19.Complications with Prognosis. 20. References 21.References for further reading[9 chapters] K.Mohan Iyer[6/7/2023]