I have been doing the practice you gave to me when you were here every day and have noticed that when I do the movement for strengthening the psoas I hear/feel/sense this knocking sound. I start by rotating the left leg at the hip so the foot is turned outward, then raise it up and out at 45 degree angle. As I lower the leg I hear this knocking sound just before the foot returns to the floor. I also sometime sense the same thing as I rise the leg in the spine around what I suspect is the attachment of the psoas. I tried the same movement with the other leg and don’t get this sound. Since it’s my left piriformis/sacrum that has been causing some discomfort, I was just wondering what might be going on and if I’m doing the movement right. I don’t hear the sound if I lift the leg straight up toward the ceiling but if I rotate the foot out and then lift it straight up toward the ceiling, I do hear this knocking.
Sounds like psoas is weak, I recommend doing the same motion only lift maximum of 12 inches. Also do the sunbird pose with knee bent out to the side (some call this the dog at the hydrant pose). This will strengthen the piriformis often reacting to weakened psoas.