There are actually a lot of points there- all the leg meridians except kidney have a point along that line/arc across the front of the ankle. Boot is completely nasty. Scrape kick or stomp down and into the small bones below the points. If you keep standing on the foot and take the person down backwards, you should be able to get a fracture. You can also cut into those points with either ridge or blade side of your hand in grappling.
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The older I get, the better I was!