Unless there is already knee damage (torn cartilege, or other problems), forward crossovers should never cause knee pain.
Also, unless the knee is seriously damaged (and in some cases even if), some good off-ice training can help immensely. The off-ice training should focus on controlled strengthening of the leg muscles... i.e., quads, hamstrings, shins, calves. And... it's preferable to avoid weight machines such as the leg extension (normally good for quad strengthening) unless the exercise is modified to constrain the range of motion.