During my recent meditation, I noticed that every time my mind wondered, my breathing pattern changed.
If I start thinking or worrying about something - my breath becomes constrained.
If I start to drift to sleep - my breathing becomes weaker.
Before true samadhi can be experienced, a practitioner must lose awareness of his/her body. When pain or discomfort arise during meditation, we come back and lose our concentration.
Therefore, we must relentlessly heal our bodies, to be able to enter into, and remain in, the meditative state, before the body calls us back, and we are compelled to return.
With diligent, consistent practice of HeartMirror pranayama, your mind will become better at entering, and remaining in, the meditative state, regardless of the disruptive signals from your body and your restless heart.
Think of it as a handy short-cut: you don't have to wait for your body to be healed to the point of not sending out disruptive aches, pains, and twinges.
You can experience Zen-like concentration now - and fix that knee later!