Science? Ok, so present the scientific evidence of the repairing effects of MK-677. Yes, there are anecdotal evidence of joint repair from GH, as there are equal amount of anecdotal evidence of joint pain and stiffness from GH. Does it increase collagen synthesis? Yes, but so does anabolic steroids. But I still haven´t seen a single study showing it´s strengthening effects on connective tissue.
There is this 2013 study though:
J Bone Joint Surg Am. 2013 May 1;95(9):783-9. doi: 10.2106/JBJS.L.00222.
Human growth hormone may be detrimental when used to accelerate recovery from acute tendon-bone interface injuries.
Baumgarten KM1, Oliver HA, Foley J, Chen DG, Autenried P, Duan S, Heiser P.
By the way. My effed up joints are mostly due to plica syndrome, an abundance of joint tissue and has nothing to do with degeneration. My ligaments are strong as steel and have held up perfectly during decades of hockey, BJJ, MMA and powerlifting. There are 4 ligaments in the knee. I tore the "LCL, not the "ACL". Could it have been a coincidence? Maybe. But it definately raised my attention.
Look, if you are one of those guys who refuses to accept that extrapolation can lead to reliable conclusions, there is nothing I can say to you. In this case you might as well argue that GH doesn't increase muscle growth. Actually, you should just take it a step further and argue that SD doesn't build any muscle tissue either. After all, there has never been a single human study showing that SD--or about 200 other steroids--are capable of building muscle mass in humans, yet we know for a fact they do. Obviously, if we can draw conclusions like this with SD based on both anecdotal evidence and scientific extrapolation, then it is also possible to do with other drugs.
Now, you could sit here and continue to say
"I am going to deny that MK is capable of stimulating tendon regeneration until I see a study specifically showing that it does", but I won't argue about something that doesn't exist. Just like I won't argue with someone who says that I can't claim SD causes muscle growth in humans because no studies exist, neither will argue with someone who says that naturally produced GH (MK-677) doesn't stimulate tendon/connective tissue regeneration--because we already knows that this is one GH's primary functions in the body. .
Now, extrapolation obviously isn't reliable in all cases, but there are times in which it is. In the case of MK-677 I would say it is pretty reliable for multiple reasons, so let's see why.
As you know, studies show that GH can greatly increase collagen synthesis. However, there are multiple types of collagen produced by the body, all of which have different functions. The good news is that GH increases production of the specific type of collagen that assists in the regeneration of tendons. Being that MK also increases GH levels, it is reasonable to conclude that it would increase the production of the same type of collagen and therefore stimulate tendon regeneration...just like exo. GH.
Of course, we also need to look at the amount of GH required to have this effect, to make sure MK-677 is capable of elevating GH levels to the same degree as those seen in the exo. GH studies. How much GH does it take to have this effect? Research has shown that even 1-2 iu of exo. GH significantly increases collagen production...and 3 iu led to a dramatic increase. MK-677 is capable of increasing GH levels the equivalent of 3 iu of exo. GH...and in some cases even more.
You mention the fact that AAS have also been shown to increase collagen production, but comparing AAS to MK-677 is inaccurate for a few reasons. For one, not all AAS increase collage synthesis. In fact, many drastically reduce collagen synthesis. Just 300 mg of testosterone/week (I could be off on that number, as it has been year since I read the study, but I know it's close) has been shown decrease collagen synthesis by up to 80%. That is a LOT--similar to an 80 year old man! Furthermore, even if a steroid does increase the production of the right type of collagen, it still will not have the same effect. This is because steroids do not build structurally sound connective tissue like GH does. Winstrol is perhaps the most well known example. Although Winstrol has been shown to increase collagen synthesis significantly and build bigger tendons, it causes what is known as cross-linking (improper formation of connective tissue). This cases the tendons to get bigger, but they also become WEAKER and more prone to in jury. This is why so many tendon injuries occur while using Winstrol. There is is no denying that Winstrol will build tendon size, but it sure doesn't make them stronger--it makes them weaker by decreasing their structural integrity.
GH does not and has never been shown to have this effect.
So, when you compare AAS to GH you are comparing apples to oranges, but when you compare GH to MK-677, you are comparing apples to apples because both drugs increase the exact same hormone with the exact same functions. Both are human hormones (not synthetic aberrations like AAS, which produce unnatural effects). In fact, MK causes the release of real, naturally produced GH. So, we can reliably conclude that exo. GH and pituitary produced GH (MK-677) both have the same effect, as exo. GH is bio-identical to the GH produced by the pituitary.
In terms of anecdotal evidence, bodybuilders and especially athletes have known for decades that GH promotes tendon regeneration. This is the main reason that athletes use it. It helps keep them in the game longer and increases their chances of remaining injury free. In fact, the real-world evidence for GH's positive effect on tendons/connective tissue is so vast that it is almost impossible to deny. In combination with what science has already revealed about GH and its effects on the tendons, it stands to reason that any drug (MK-677) that substantially increases GH levels would have the same effect.
Lastly, real-world evidence has shown, with ever increasing frequency, that MK-677 has the same kind of beneficial effects on connective tissue that GH does. This is not surprising, as the level of GH shown in studies to greatly increase collagen production is easily replicated by MK-677.
So, while no studies exist showing that MK-677 aides in tendon recovery/growth (just like no studies exist showing it increases muscle fullness or a muscle pump, even though we know it does), we do know that GH (which MK directly increases) does have this effect, as it is one of this hormone's main roles in the body.