Testosterone makes you stronger than you otherwise would be. Everyone knows that. What some people dont know is that while your muscles get stronger, your ligaments and tendons do not. They remain the same. So while we are pushing and pulling more weight in the gym, we are putting stresses on those tendons that would otherwise be under less strain. The result is overuse and sometimes damage to ligaments and tendons. Whereas this effect is more pronounced in individuals taking supra-physiological amounts of testosterone and other anabolic steroids, I firmly believe that this effect can happen within the realm of trt. I am on trt, and I have noticed this myself. The 160mg/week of t-cyp that I take puts my t levels about 800-900 points higher than I would be if I wasnt injecting. As a result I can see a marked difference in the amount of weight I can lift, especially on the core exercises like benching and squatting. I can 100% tell a difference. The problem is if im not catefull and try to go too heavy, I end up with very sore knees, or particularly a very bad case of tendonitis in my right elbow. And lastly, I dont think estradiol has anything to do with this particular issue, like some previous posters have suggested. Estradiol is very important and has its' roll in trt of course, but I have noticed that alot of us seem to attribute every little problem we have while on trt to estradiol being not ideal. Its just not the case.