I am in a similar situation at a similar age with a bad knee that started taking abuse in the military. Despite feeling my age a little more every day the rest of my body still wants to win tournaments. I am enjoying the advantage of experience, timing, and focus that I have over most folks. With my frequently gimpy knee (and other joints) I have a feeling that I only have a limited number of fights left in me and want to make the most of them.
I do not feel that I have found a "magic bullet" yet but I do seem to be doing better than my peers and even hard fighters fifteen years younger. 1) I have personally seen more harm than good from knee surgeries and I am not willing to accept those odds until I cannot move at all. 2) Exercises to develop supporting muscles seem to help a lot (if you rememember to keep up with them every day) like:
These seem to build a stable "cup" of muscles under the knee. I have gotten at least one friend off the knee surgery list with this. 3) Practice good knee habits like not crossing your legs when you sit down. Warming up before you stretch before you practice. Drink more water. Bicycle. 4) I avoid pain meds. They just treat symptoms. Pain is nature's way of telling you what not to do to make things worse. I have come to trust veterinarian medicines much more than human. No one cares how a horse "feels" just how fast it runs or how steady its gait is. Check out the liniments at your local tack and feed shop. Research DMSO.
I am always looking for other practical tricks.
Dave, congratulations on your diligence and pursuing your fitness and martial arts enjoyment. I'm 50 and still train hard in both martial arts and fitness, but mostly on my own. I think the key for guys like us is abbreviated workouts (No more than 3x per week, ~30-45 minute sessions) and a LOT of recovery time. For your training purposes, I would do a heavy, strength-based workout no more than twice a week, with something like the 5x5 protocol. I would not max out on any weight exercises, and do the workout as quickly as possible to allow for some cardio, but not so quick that you cannot lift fairly heavy. I would also say never max out, and never do any weight you can't do at least twice or three times. Also do your "skills" and sparring workout no more than twice a week, and concentrate on quality instead of quantity. Make very minute count, in both your workout and skill sessions. I would also allow a day in between each workout, regardless of if it is skill or weight based.
An excellent reference book for older lifters is "Gray Hair and Black Iron" by Brooks Kubik, author of Dinosaur Training. Great workout ideas for us older guys.
Good luck, and I think you will do well.
Work on explosive cardio and back off on the roadwork. Roadwork is good for general fitness, but works against your flexibility and doesn't contribute to the start-stop kind of conditioning you'll need for the ring. It sounds like you're pretty fit anyway and weightloss isn't a major concern. I'd recommend short intense runs - e.g. a quick 1/4 mile jog, then sprint between telephone poles, jog to the next pole, then sprint again, jog, sprint, jog, etc. When you're just about winded wind down with a final 1/4 mile jog.