Hi there, first things first, I would suggest having that checking out that knee pain to make sure it's a strain and nothing more serious. I strained the ligaments of the knee last month and consulted a Eu Yan Seng tcm practitioner for some herbal wrap and it did get better with much rest and the use of a knee support. The TCM practitioner told me that its good that I went to get it checked out as a ligament strain takes a longer time to recover from compared to a muscle strain.
If you really want to exercise in the mean time, you may consider low impact exercises such as swimming. Inspire Mums & Baby has aqua pilates and aqua yoga.
http://www.inspiremumbaby.com/