The elbow x-ray shows haemathrosis as evidenced by elevated anterior & posterior fat pads. There is an undisplaced olecranon fracture. The radio-capitellar line is disrupted, indicating the presence of a radial head dislocation.
Radial head dislocation can be difficult to appreciate on the AP view but easier on the lateral as in this case. Radio-capitellar line helps in the detection of these injuries. This line is drawn along the long axis of the proximal radius. The line should pass through the capitellum on every view. If not, the radial head is dislocated.
Reference: Grainger & Allison’s Diagnostic Radiology, 6th Edition