Your question has lots of open answers. What is the etiology of the knee pain? What are the cardiovascular issues? What are the diagnoses and prescriptions of the physician(s?) A pool is certainly a conducive environment for a number of strengthening/flexibility exercises. Just work within the guidelines prescribed by the attending physician.
If you aren’t training runners using aquatic exercise, you are missing some of the best training opportunities for your clients.
I am an advocate of aqautic exercise for restrengthening injured runners and athletes. I also use it to train my clients that are not injured. Aquatic exercise is used in almost all professional sports programs for prehab, rehab and postrehab situations. And equestrian (horses) training facilities spend big money to construct pools/tanks for use to train multi-million dollar horses, both as training and rehab for injuries. It is even possible to train for power and hypertrophy using aquatic exercise.
If you think that aquatic exercise is too wimpy for you, I invite you to visit me on the Big Island of Hawaii. I’ll change your mind. This is one of the course formats that I teach as CECs for fitness professionals. Check out my website – www.hawaiifitnessacademy.com . And I would be happy to just meet any fitness professional coming here on vacation. This is my passion and I like to spread the Aloha in the fitness community.
Knee pain, as multiple people have mentioned, could have a variety of sources. I would suggest visiting your doctor and seeing if he or she thinks that Physical Therapy might be a good idea. From personal experience, PT did not work for me. I have found that running is not tolerable, on a long-term basis. On the other hand I have found upright or recumbent cycling, incline treadmill walking, hiking, or elliptical machines to be very tolerable.
Unfortunately, we don’t have it all figured when it comes to knee pain. While Physical Therapy can be great and may work well for you, I’ve also seen it fail to decrease pain in others. I hope that you find something that works for you!
It really depends on the problem. Knee pain is very vague. Let me help you narrow it down. Where on the knee is it hurting(front, side, back)? What kind of pain is it (dull, sharp, burning)? Is it a chronic pain or an acute pain? What movements cause you the most pain?
Depending on how you answer any one of these questions will lead to a different type of training, but in general non load bearing cardio would probably be best.
I suggest you have a thorough functional/mobility assessment done for your hip and ankle. Most problems that are not caused by direct trauma are related to issues/compensation patterns in the kinetic chain.
1. Find out what the cause of the knee pain is.
2. Get it resolved.
3. Go back to doing the cardio you enjoy.
4. Make sure you avoid what caused the knee pain.
On another note…
I personally enjoy Kangoo Jumps, the take the stress off my knees.