For ten points, what legbone forms a ball-and-socket joint with the hip.
The proximal end is rounded for articulation with the acetabulum;  distally, it expands into two condyles, below which lie the medial and lateral menisci.  Near the proximal end are trochanters for muscle attachments, including the gluteus medius and minimus.  For ten points, what legbone forms a ball-and-socket joint with the hip.
The proximal end is rounded for articulation with the acetabulum;  distally, it expands into two condyles, below which lie the medial and lateral menisci.  
femur or thighbone