1 00:00:00,080 --> 00:00:02,080 Speaker 1: This episode of brain Stuff is brought to you by 2 00:00:02,120 --> 00:00:05,519 Speaker 1: Linda dot Com. Linda dot Com offers thousands of engaging, 3 00:00:05,559 --> 00:00:08,760 Speaker 1: easy to follow video tutorials taught by industry experts to 4 00:00:08,800 --> 00:00:12,440 Speaker 1: help you learn software, creative and business skills. Membership starts 5 00:00:12,440 --> 00:00:16,000 Speaker 1: at twenty five a month and provides unlimited seven access. 6 00:00:16,120 --> 00:00:18,720 Speaker 1: Try Linda dot Com free for seven days by visiting 7 00:00:18,840 --> 00:00:22,960 Speaker 1: Linda dot com slash brain Stuff. Welcome to brain Stuff 8 00:00:23,079 --> 00:00:33,839 Speaker 1: from how Stuff works dot com where smart Happens. I 9 00:00:33,960 --> 00:00:38,040 Speaker 1: am Marshall Brain with today's question, what makes your knuckles pop? 10 00:00:38,640 --> 00:00:41,879 Speaker 1: If you've ever laced your fingers together, turns your palms 11 00:00:41,920 --> 00:00:44,520 Speaker 1: away from you and bent your fingers back, you know 12 00:00:44,640 --> 00:00:49,120 Speaker 1: what knuckle popping sounds like. Joints produced that crack when 13 00:00:49,280 --> 00:00:53,400 Speaker 1: bubbles burst in the fluids surrounding the joint. Joints are 14 00:00:53,440 --> 00:00:57,400 Speaker 1: a meeting point between two separate bones, held together and 15 00:00:57,640 --> 00:01:01,520 Speaker 1: in place by connective tissues and ligaments. All of the 16 00:01:01,600 --> 00:01:05,399 Speaker 1: joints in our bodies are surrounded by synovial fluid, a thick, 17 00:01:05,560 --> 00:01:09,039 Speaker 1: clear liquid. When you stretch or bend your finger to 18 00:01:09,120 --> 00:01:12,520 Speaker 1: pop the knuckle, you're causing the bones of the joint 19 00:01:12,560 --> 00:01:16,280 Speaker 1: to pull apart. As they do this, the connective tissue 20 00:01:16,400 --> 00:01:21,240 Speaker 1: capsule that surrounds the joint is stretched. By stretching this capsule, 21 00:01:21,319 --> 00:01:25,000 Speaker 1: you increase its volume, and, as we know from chemistry class, 22 00:01:25,160 --> 00:01:28,560 Speaker 1: with an increase in volume comes a decrease in pressure. 23 00:01:29,000 --> 00:01:32,479 Speaker 1: So as the pressure of the synovial fluid drops, gas 24 00:01:32,640 --> 00:01:36,240 Speaker 1: is dissolved in the fluid become less soluble, forming bubbles 25 00:01:36,280 --> 00:01:40,280 Speaker 1: through a process called cavitation. When the joint is stretched 26 00:01:40,319 --> 00:01:43,679 Speaker 1: far enough, the pressure in the capsule drops so low 27 00:01:43,760 --> 00:01:47,480 Speaker 1: that these bubbles burst, producing the pop that we associate 28 00:01:47,560 --> 00:01:51,720 Speaker 1: with knuckle cracking. It takes about five to thirty minutes 29 00:01:51,800 --> 00:01:55,280 Speaker 1: for the gas to redissolve into the joint fluid. During 30 00:01:55,280 --> 00:01:59,120 Speaker 1: this period of time, your knuckles won't crack again. Once 31 00:01:59,160 --> 00:02:03,240 Speaker 1: the gas is dissolved, cavitation is once again possible, and 32 00:02:03,360 --> 00:02:06,560 Speaker 1: you can start popping your knuckles again. As for the 33 00:02:06,720 --> 00:02:11,520 Speaker 1: harms associated with this habit, according to Anatomy and Physiology 34 00:02:11,560 --> 00:02:16,440 Speaker 1: Instructors Cooperative, only one in depth study regarding the possible 35 00:02:16,560 --> 00:02:21,200 Speaker 1: detriments of knuckle popping has been published. This study, done 36 00:02:21,200 --> 00:02:25,240 Speaker 1: by Raymond Broder and published in the Journal of Manipulative 37 00:02:25,360 --> 00:02:31,280 Speaker 1: and Physiological Therapeutics, examine three hundred knuckle crackers for evidence 38 00:02:31,280 --> 00:02:35,560 Speaker 1: of joint damage. The results revealed no apparent connection between 39 00:02:35,639 --> 00:02:40,880 Speaker 1: joint cracking and arthritis. However, habitual knuckle poppers did show 40 00:02:40,960 --> 00:02:45,359 Speaker 1: signs of other types of damage, including soft tissue damage 41 00:02:45,400 --> 00:02:48,800 Speaker 1: to the joint capsule and a decrease in grip strength. 42 00:02:49,280 --> 00:02:52,200 Speaker 1: This damage is most likely a result of the rapid, 43 00:02:52,280 --> 00:02:55,800 Speaker 1: repeated stretching of the ligaments around the joint. On the 44 00:02:55,840 --> 00:03:00,240 Speaker 1: positive side, there's evidence of increased mobility and joints right 45 00:03:00,280 --> 00:03:04,920 Speaker 1: after popping. When joints are manipulated, the gold g tendon organs, 46 00:03:05,040 --> 00:03:08,400 Speaker 1: a set of nerve endings involved in humans motions, sense 47 00:03:08,800 --> 00:03:12,000 Speaker 1: are stimulated and the muscles surrounding the join to relax. 48 00:03:12,480 --> 00:03:14,959 Speaker 1: This is part of the reason why people can feel 49 00:03:15,040 --> 00:03:19,280 Speaker 1: loose and invigorated after leaving a chiropractor's office where a 50 00:03:19,400 --> 00:03:24,320 Speaker 1: cavitation is induced as part of the treatment. Backs, knees, elbows, 51 00:03:24,400 --> 00:03:27,400 Speaker 1: and all other movable joints are subject to the same 52 00:03:27,520 --> 00:03:31,480 Speaker 1: kind of manipulation as knuckles are. Do you have any 53 00:03:31,560 --> 00:03:35,200 Speaker 1: ideas or suggestions for this podcast? If so, please send 54 00:03:35,200 --> 00:03:38,520 Speaker 1: me an email at podcast at how stuff Works dot com. 55 00:03:38,640 --> 00:03:40,880 Speaker 1: For more on this and thousands of other topics. Go 56 00:03:41,000 --> 00:03:43,800 Speaker 1: to how stuff works dot com and be sure to 57 00:03:43,880 --> 00:03:46,120 Speaker 1: check out the brain stuff blog on the how stuff 58 00:03:46,120 --> 00:03:52,240 Speaker 1: works dot com home page. 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