olecranon; tip of the elbow
Anatomical term for the bony prominence at the back of the elbow. In everyday language, 肘の先 or 肘の骨 is more common.
Olecranon fractures are likely to occur when falling.
The doctor diagnosed it as olecranon bursitis.
Compound of 肘 (elbow) and 頭 (head/tip), literally 'elbow head'. The reading ひじがしら follows standard kun'yomi for both characters.