[gemy]

IMO clunking is a pretty descriptive term that is quite different to a popping or a clicking sound.

Clunking immediately brings to my mind the hip joint and not the knee joint.

So Doc Martin, when you extend her back leg are you doing so from above the knee joint? Meaning her foot is hanging relaxed the knee neither needs to flex or extend, so that you are holding above her knee when you take that upper thigh back. If so then the hip is more likely.