I'm no specialist when it comes to supps or medication, so I'll just address the training-aspect of things:
A) Avoid tendon-unfriendly exercises such as skullcrushers or alter the way you do them
B) Don't go crazy with the volume and/or frequency
C) do some "cruising" for a while, avoid intensity techniques, use somewhat less weight, don't go to failure... Or even take time off or include more off-days in your routine. Less often necessary when training with a regular modern bb routine with standard frequency.
However, if you've made great strength gains over a relatively short period of time, it would be wise to remember that the joints and tendons don't have much of a metabolism of their own and don't adapt nearly as fast as your musculature. Most guys never make progress that fast anyway, but yeah.
D) Higher rep ranges for a while can help, especially for older guys
E) Look at the overall workload... Just because you're never going to failure doesn't mean doing 4+ sets at 85-90 percent or whatever of your 1RM is suddenly joint-friendly.
F) Check your exercise technique in general
G) If you went low or no-carb for a while, reintroduce some carbs into your diet. If you went low-fat, get in more fat. And then there's fish-oil, I guess, but I don't know how much of a difference that actually makes. The only actual tendon/joint-supp I've taken thus far was some seashell extract thing...
I had what I believe were somewhat irritated forearm tendons (near the elbow). Trouble went away the very next day, but I wasn't direly injured or anything to begin with, so take that for what it's worth.
I'm sure bushidobadboy, Sento and co will be able to give you more helpful answers.
(what I mean with exercise technique: If you are, say, dropping the bar towards your feet to some degree or so while pressing... That can pose serious strain on your arm flexors and elbows in general... That kind of thing, among others)
I think in your particular case you just need to take it down a notch for a while though. Instead of going 3 out of 5, make it 3 out of 7 and maybe do an exercise less here or there for 2 weeks or so... Non-failure and what have you, maybe go somewhat lighter and then work back up...
I'm 39 and my joints started aching consistently a few years ago. The joint fuel type supplements with glucosamine really help but you really have to take them consistently and give them a week or so before it starts to help. High doses of fish oil made a big difference in joint pain too, along with several other benefits, but I have issues with my blood not clotting quickly when I get the doses high enough to make a difference.
as far as supplements go, i think glucosamine (joints) and cissus (tendons) are supposed to help. i havent used either as i have neither of these problems, but i hear cissus is very good, especially for things such as elbow tendonitus.
i imagine you will get a lot of advice to mega dose fish oil as well, for anti-inflammatory as well as other benefits.
what is the rationale behind this? i have heard it before with regards to fat, but less in connection to carbs. do you mind explaining the benefits of carbs in this situation i would greatly appreciate it.
I know several people personally who tried keto-diets and found that adding carbs back in suddenly made their joint-troubles disappear, so that's why I'm mentioning it. We've also had a few such cases on the boards I think...
Hey, the few joint-supps I know of seem to be carb-based, too, come to think of it.
I'm hoping that BBB or Sento will chime in here...
I was taking I think 15 to 20 grams a day then. I felt great, it cleared up my dry elbows, energy level was way up. The only problem was even small cuts took a while to clot. My wife is a nurse and she put the fear into me that if a got into an accident or something and had some internal bleeding it might be a problem. I still take it but I keep it around 10g a day.