"Phut", the sound of a twig breaking, which I heard when I was 18, changed my life to a large extent. This was the sound of my ligaments in the left knee breaking/stretching, while I executed a twisting kick during my Tae Kwon Do practice. This injury left me with an unstable and painful knee which couldn't support me on lateral movements. I consulted several orthopedics and also a sports medicine specialist, who suggested arthroscopy to repair these ligaments to bring this back to normal. For all those who don't know, ligaments are like rubber bands, once they break or stretch beyond their normal range, it cannot be reversed.
One doctor suggested that I live with it and change my life preferences (read stop practicing TKD) and live a regular less active life (read couch potato). Not for me. I decided to try PT and see how much it helped me regain my normal strength in the knee (i understood that to support a weak body part, I would need to strengthen the muscles around it). Since then I have been regularly gymming with an emphasis on leg extensions and curls and also progressed onto weight bearing squats. This enabled me to feel a lot better and I could go back to my active ways of walking, cycling, swimming and trekking, feeling the occasional pain. Of course I cannot run for long and cannot practice TKD anymore.
Last 2 years however have seen another major turn point. I took to very long distance cycling, which involved hundreds of kilometers at a stretch for days on end. This put an all new burden on my knees and here is where I was lucky to try Yoga at Param Yoga. Its amazing how holding the poses builds strength in the entire body and it happens "invisibly". Means the body doesn't grow or may not shape up, but internally the organs, the musculature and joints become very strong. "Magically" due to the consistent practice, my lower back soreness (due to long sits in the saddle) is gone, my nagging knee is much better and allows me to pedal more than 100 kms a day, my trap muscles between my shoulders have relaxed a lot, and overall I saw a major shift in my capacity to endure the rides and normal ADL (activities of daily living).
As a side note: I am not recommending one form of exercise over another. Instead I am recommending the right proportion of multiple forms of exercise to achieve a balance in mind-body fitness. The proportions depend on your goals...E.g. if you want to be a swimmer, the proportions will be biased towards endurance and strength, if you want to be a runner, it may be biased towards cardio and weight management, and so on.
As of today, while I am biased towards Yoga, I also add in one day a week of specific gym work and also 1-2 days a week of hill climbing (besides the long rides). The cross training actually gives an "active rest" to the overused muscles. The combination of the 3 prepares me for my long rides.
Heres an article written by Dr. Renu Mahtani, founder of Param Yoga, on the health of knees and yoga.