Angela, most believe that Caffeine in moderate amounts is not harmful and may even be beneficial to you. The Caffeine jolt you and I are so fond of of, kinda perks up the bodies nervous system and can provide temporary relief from general fatigue. Excessive caffeine, however, has been blamed for many health issues, including joint pain.
Too much caffeine can cause sleeplessness (insomnia), stomach distresses, and, rapid (and sometimes) irregular heartbeat. Some think that muscle tremors can be caused by excessive caffeine and supposedly muscle tremors can put stress on the joints and can cause pain.
Caffeine is also thought to possibly weaken bone massive and therefore cause joint pain.
Aside from not being able to sleep, some people report restless leg syndrome from drinking caffeine. And hold on to your hats,.... this is worse when you drink coffee or other caffeine products just a few hours before bed time. How Bat Guano, Batman,...do you think?
However, I am an avid coffee drinker. I'm sure that one of my cups is the equivalent to several of yours in caffeine content. A double red eye (coffee with two shots of expresso) from Starbucks is my normal drink when I am on the road and can't make my own. My knee pain from years of over use in the military and other endeavors is greatly diminished to the point where I only rarely even get a twinge. I believe this is from the pharmaceutical grade Glucosamine and nutritional supplements I take daily. Based on the amount of coffee-caffeine I consume, I would think that if caffeine is bad for joints then I would know about it.
However, everyone is different. There is a study from Science Daily, March 30, 2009 showing that caffeine may help one in exercise or other physical activities.