Lie supine on floor or mat. Raise knees and grasp back of thighs behind knees.
Pull knee toward shoulders or to side of torso while keeping opposite leg on floor. Hold stretch.
Keeping lower leg straight keeps pelvis from tilting so upper knee does not have to come back as far. Gluteus Maximus is stretched if hips are slightly external rotated. Piriformis and Quadratus Femoris become stretched if hip is slightly transversely adducted (knee toward opposite side of chest).
Other (see notes)