First Meridian Therapy Session - extreme discomfort next day. Is this normal?

While this is not really related to Chinese Medicine in any way, I’ll offer what I can. Deep tissue therapies can frequently be quite painful. My guess is that she was trying to loosen your IT band (which is tight on many people) to take tension away from the knees. This can certainly lead to soreness for a few days following a treatment. It may happen the first few times, but after that with communicating with your practitioner about your response they learn (or good therapists do anyhow) what your body can handle and what it can’t. After some of the initial opening happenings and your therapist knows how your body responds these stronger responses should not happen.

There are a host of things, however, that can go wrong with aggressive techniques and if you have pain that doesn’t go away in a couple weeks and/or it keeps happening after more than 3 treatments I would stop seeing that therapist and consult with your medical doctor for proper evaluation.