The acetabular fossa is the non-articular depressed region at the centre of the floor of the acetabulum.

[1]: 1368 [2] The floor of the fossa is formed mostly by the ischium;[2] it is rough[1]: 1354  and thin (often to the point of transparency).

The space of the fossa is continuous inferiorly with the acetabular notch.

[1]: 1368  It is occupied by the ligament of head of femur,[3][better source needed] and by fibroelastic adipose tissue[4][1]: 1368  (within which the acetabular branch of the obturator artery ramifies[1]: 1250 ) that is mostly lined with synovial membrane.

[1]: 1368  The acetabular "fat pad" is thought to contain abundant proprioceptive nerve endings that sense compression of the fat pad or its displacement through the acetabular notch, producing proprioceptive information.