<prompt> Commonest site of tuberculosis is:Hip jointSpineKnee jointAnkle joint  <response>: Spine: Ref: 387-A The spine is the most common site of skeletal tuberculosis and the most dangerous Blood borne infection usually settles in a vertebral body adjacent to the intervertebral disc. Bone destruction and caseation follows, with infection spreading to the disc spaces and to the adjacent vertebrae. As the vertebral bodies collapse into each other, a sharp angulation or kyphos develops. Caseation and cold abscess formation may extend to neighbouring vertebrae or escape into the paravertebral soft tissues. There is a major risk of cord damage due to pressure by the abscess or displaced bone or ischaemia from spinal artery thrombosis. 