The sacroiliac joint (SIJ) has gained its importance towards anatomical and radiological studies in relation to the treating aspects in ankylosis and other degenerative diseases of the joint. This complex joint shows numerous structural variations with the increase of age. The present case describes a pelvic bone showing the ankylosis of SIJ and the ossification of sacrospinous (SSL), sacrotuberous (STL) and transverse acetabular ligaments (TAL). The postero-superior interosseous part of the SIJ was completely fused, and the anterior and posterior sacroiliac ligaments were ossified. The SSL of the right side was completely ossified. Left SSL and both right and left STL were partially ossified. The TAL of both sides were also completely ossified. These ossified structure as found in our case may impede the movements of the joints of pelvic bone and results in the pain. The ossification of SSL and STL is of clinically significant because, it may compress the pudendal neurovascular bundle passing in between these structures. Anatomical and radiological knowledge of ankylosis of SIJ and ossification of the ligaments as found in the present case may be helpful for clinicians, radiologists and surgeons for differential diagnosis and can be implicated in the development of innovative treatments of sacroiliac and perineal pains.
