This is an advanced version of the doorway lat stretch which applies a further stretch to the posterior chain.
Stand in front of a doorway with your feet hip-width apart.
Reach one straight arm up and hold the door frame at roughly shoulder height.
Turn your body towards the raised arm such that your raised arm is now slightly crossing in front of your chest.
Gently step the leg on the same side as the lifted arm back and across your body on a diagonal, bending the supporting leg into a curtsey lunge position.
Gently lean into the curtsey lunge until you feel a stretch along the side of your body and under your arm.
Hold/maintain as prescribed by your physiotherapist.