There are many studies with Vitamin K2, though most are for age related osteoporosis/arterial plaque prevention. Since it prevents plaque deposits that suggests it would work even for inactivity caused bone loss, but thats only supposition. Spend some time on google to learn more, and also check out vitamink2.org
Just to save you some time for maximum bone effect you need at least about 360mcg of MK7 or 1000mcg of MK4. Its likely MK4 does more then MK7 but is more costly and needs a higher dose. My non medical but highly researched opinion is that 2mg of MK4 would be ideal, if you can get it. When i had money i used Thorne MK4 drops, 2 drops a day on a meal with fat/protein (eggs, meat, peanut butter etc). If you have wisdom teeth that are unerupted it will push on them which is painful if your jaw has no room for them to come out (its actually what causes wisdom teeth to come out in normal humans but we are designed to have this vitamin all our lives including our growth years which would have had no pain). I'm not sure if MK7 will do this or not. If you have had your wisdom teeth removed or they have already come out (rare) or your jaw has the space then your fine.
It also has many other effects that are under research, unspecified immune effects, is found in the pancreas, kidneys and brain but its roles there are unknown (though its required for sphingolipid production which is interesting given Dr Davis mentioning of sphingolipid abnormalities, though the relationship is undetermined) and so forth.
I have not found it to have a big effect on my ME/CFS but there is no evidence it has any direct connection to our symptoms so thats not too surprising (though of course i wish it was a ME/CFS cure)