I sew on the Bekant sit/stand desk from Ikea that Mombygrace linked to. I love it, and find I have much less shoulder and back pain since I got it. If you get the power-adjustable version, I have found that it will sometimes not raise smoothly if I leave my machine sitting towards one end. It will go up an inch, then stop. Taking the machine off for an hour, or setting it in the middle of the table instead of more over one leg, fixes the problem.
An adjustable table like this is also great for cutting at the perfect height, and really anything else you do. I use mine at 5 or 6 different heights on a regular basis, just depending what I am working on. I like that I can adjust it half an inch if I want... sometimes the smallest change can make a huge difference.
Like others have said, try to see an OT as well as the PT. The occupational therapist will be best equipped to give you ergonomic advice.