When measuring leg extension / flexion angle, where exactly do I put the pivot (vertex) of the angle on the knee? I have seen fitters use:
1) the hollow spot just behind the side of the patella
2) a point equi-distant from front to back on the side of the knee and even
3) a point on the side of the knee that corresponds with the front surface of the center of the pattella.

I've been using location 1, but now that I've seen so many locations, which is correct and how do I find it accurately?

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John