Funny you should bring this up. I have a heating pad on my shoulder as I type. Mine is a problem that come and goes, but it's aggravated by too much time at the computer with bad posture, stress, and picking up my 5 and 3 year old the wrong way. I've been finishing a major project for a class I'm taking and I should have known to take more stretch breaks!
I've find that if I take Alleve for a few days, add heat and little Aspercreme I can get the pain to subside enough for me to live life as normal.
It's better not to do the same task repetitively, so I alternate between my laptop at the kitchen bar, at my desk and my husband's computer. Maybe you could still knit if you were to watch your posture and change the project to one of a different scale?
I haven't been practicing lately (which is probably why my shoulder hurts), but yoga really seems to help my posture and build strength in my shoulder. I'll have to wait until the pain is gone, but I really need to practice more preventative medicine. I also need to incorporate the stretches that dink included.
Hopefully, we'll both be feeling well soon!