the femurs and the sacrum
The sacrum articulates with the hip bones of the pelvis.
The femur articulates with the patella, tibia, and OS coxae (hip bone). And the patella articulates with the femur only. So in all, not counting the femur and patella, two.
Proximally (towards the hip) the femur articulates (attaches to) the acetabulum which is made up of all three hip bones: the ilium, ischium, and pubis. Distally (towards the foot) the femur articulates with the the tibia and fibula.
sacrum
the rib cage
sternum
The radius articulates with more of the carpal bones than the ulna.
The metacarpals articulate proximally with the carpals. In particular, the first metacarpal articulates with the trapezium. The second articulates with the trapezium, trapezoid, and capitate. The third articulates with the capitate. The fourth articulates with the capitate and hamate. The fifth metacarpal articulates with the hamate.
The medical term for the hip socket is acetabulum.
The Sacrum and the femur articulates with the Pelvis
The metacarpals articulate proximally with the carpals. In particular, the first metacarpal articulates with the trapezium. The second articulates with the trapezium, trapezoid, and capitate. The third articulates with the capitate. The fourth articulates with the capitate and hamate. The fifth metacarpal articulates with the hamate.
It is the sacrum.