Joints like our knuckles are lubricated with liquid called the synovial fluid. When manipulated, these joints can pop or crack audibly. For half a century, researchers have thought the cracking sound joints under tension make was the result of bubbles in the synovial fluid collapsing. But a new cine magnetic resonance imaging (MRI) study shows that the sound is generated during bubble inception and that the cavity persists after the sound. When the bones of the joint are pulled, viscous forces resist their separation. With enough force, the joints separate suddenly, causing a pressure drop in the synovial fluid that forms a vapor-filled cavity in the joint. According to the real-time MRI observations, this is when the sound is generated. The cavity does eventually dissipate, they found, but only well after the pop. The whole joint-cracking process is consistent with the tribonucleation mechanism seen in machinery.  (Image credit: G. Kawchuk et al.; GIF via skunkbear, source video)

An MRI of Cracking Joints

The video above shows a subject pulling his finger in an MRI. Our joints are lubed with what’s called synovial fluid, and when you crack your knuckles, your joints separate and create more space. Essentially, there’s not enough of that fluid to fill the gap. Therefore the gas-filled above appears and is behind the sound that you hear. 


Sound Not What It’s Cracked Up To Be

Canadian researchers may have finally answered that other question about sound, the one not involving trees falling in a forest: Why do cracking knuckles make that noise?

Back in 1947, it was hypothesized that when, in the process of cracking knuckles, finger joints were slightly pulled apart, a bubble was created in the fluid between the separated bones. Imagine a tiny balloon suddenly inflating in the synovial fluid lubricating the joint between, say, the proximal phalanx and the middle phalanx of the middle finger. The sound was the bubble collapsing when the joints returned to their usual orientations.

Enter researchers from the University of Alberta, who conducted a study using a special MRI machine that actually recorded what happened inside the hands of a volunteer as he cracked his knuckles. Their discovery: The sound isn’t the bubble collapsing. It’s the bubble forming!

“Our jaws hit floor,” study author Greg Kawchuk told NPR. “This is the exact answer. It feels pretty great.”

The finding also reinforces previous research that cracking one’s knuckles does not cause arthritis.

“It’s mostly an urban myth … perpetuated by mothers who are sick of hearing their kids crack their knuckles,” said Dr. Kevin deWeber, a sports medicine physician in Vancouver. Indeed, deWeber thinks cracking knuckles might actually be good for the joints, providing a kind of cartilaginous massage.

Please Help Terry Through His Cancer Diagnosis and Treatment

This is my friend Terry, and this is real. Help him out, tumblr.

“My son Terry was recently diagnosed with a synovial sarcoma. Synovial sarcoma is an extremely rare and  highly aggressive soft tissue cancer, that has a tendency to spread to the patients lungs.

Terry had the symptoms of this tumor since the age of 14. We went to the doctors on numerous occasions, just to be ignored and told it was pain due to his being thin. Early this year, Terry went to an outside doctor who immediately noticed it was a tumor, and sent him for approriate tests. He had surgery last Wednesday, in which the primary tumor was removed. He just received the catastrophic diagnosis a few days ago, and are working to accept it. At the same time we were told thatsome of the treatment he will need, will not be covered. Including some of the important scans needed in order to properly stage and treat this disease.”

Chondroitin, Glucosamine And Quercetin Helpful For Osteoarthritis

A new 2009 Japanese study finds a combination supplement of 1200 mg glucosamine hydrochloride, 100 mg of chondroitin (from 300 mg shark cartilage), and 45 mg of quercetin, taken daily, is helpful as a treatment for osteoarthritis. Forty-six osteoarthritis and twenty-two rheumatoid arthritis patients were given the glucosamine chondroitin quercetin supplement orally for 3 months. The osteoarthritis patients showed a significant improvement in pain symptoms, daily activities (walking and climbing up and down stairs), and changes in the synovial fluid properties. No such effects were observed in the rheumatoid arthritis patients.

   Comments: Over the past few years there have been numerous studies regarding the role of glucosamine and chondroitin as a treatment for osteoarthritis. Most, but not all, studies show these natural nutrients to have a benefit. Quercetin supplements are available by themselves and can be taken together with a joint formula that has chondroitin and glucosamine. See 


26 April 2015

Finger Clicking Good?

Many people can ‘crack’ or ‘click’ their joints but the science behind the sound – so irritating to some of us – had never been elucidated. Now researchers have used cine MRI [moving scans] to visualise knuckle cracking. By pulling on a finger, the joint surfaces were seen to separate suddenly, and as there isn’t enough fluid to fill up the increased space, air gathers within the synovial cavity. This air-filled space is created at the same time as we hear the ‘crack’ and the whole process (seen here) happens in about 300 milliseconds [the blink of an eye]. But this bubble of air doesn’t burst as previously thought; instead, it persists and gradually disappears. Continually cracking your joints was said to play a part in joint degeneration, but so far this hasn’t been shown. Cracking your knuckles may even have therapeutic benefits – although not necessarily for those in earshot.

Written by Katie Panteli

Video by Greg Kawchuk and colleagues
University of Alberta, Canada
Originally published under a Creative Commons Licence (BY 4.0)
Research published in PLOS One, April 2015

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Fun Facts About Chickens You Didn’t Realize You Wanted to Know!

As I’m cramming for finals, we reached the point in anatomy where we finished small and large anatomy, and are now on a few lectures about chickens.  As we went through all their (odd) systems, there were several times where I stopped and thought, “That’s kinda cool!” So I complied a random list of kinda-cool things I learned about chickens in the few lectures we had. Maybe you’ll find them interesting too! 

1) Poultry necks are crazy flexible. Most species have neck (cervical) vertebrae that form a joint with their skull called the alanto-occipital joint, which looks this: 

(image from 

Well in birds, there is only a single occipital condyle (instead of two), and it the atlas that it connects to is just a ring. Plus, each vertebra connect with each other via synovial joints (instead of discs like us). This gives the head and neck HUGE mobility, like you see in this gif:

2) It’s hard to choke a chicken. No, seriously. The cartilages around the trachea in poultry have complete rings, and they have a great deal of rigidity. These cartilages can even be replaced by bone. How cool is that?

3) Their respiratory system makes your respiratory system look pathetic

You know what’s cooler than exchanging gases during inspiration? What about being able to exchange gas during inspiration AND expiration? Poultry have air sacs along with lungs, which allows their respiratory system to be crazy efficient. No wonder anesthesia is so tricky for these guys.   

4) Wishing on a Wish Bone- What’s it even for?. You know that bone that you and your brothers fight over at Thanksgiving to break when the turkey is roasting?

 That’s a bone called the furcula, which with the scapula and coracoid bone (and the suprcoracoid muscle), is responsible for lifting the wings. 

Birds are a bit odd, but they are pretty cool too. 

So this bump came up last night. It’s soft, feels fluid filled. My mom, a former RN (are you ever really done being a nurse, though?) thinks it is a ganglion cyst, aka a Gideon’s Cyst or Bible Bump. If that’s what it is, then it’s just a bubble of synovial fluid that has leaked out of the joint capsule.
It’s weird, and I really want to stick it with a syringe and drain it…
Body, can you just stop doing weird stuff?

Rheumatoid Arthritis & Cannabinoid Agoinists:

“The present study suggests that a selective (cannabinoid) CB2 agonist could be a new therapy for rheumatoid arthritis (RA) that inhibits production of inflammatory mediators … Administration of (a selective CB2 agonist) to CIA mice reduced the arthritis score, inflammatory cell infiltration, bone destruction, and anti-CII IgG1 production.”

- Researchers S Fukuda et al., Dept Medicine & Rheumatology, Japan

Note: 1) Some meds have these effects too.  

2) Studies indicate RA patients may be at an increased risk of respiratory disorders, and smoking marijuana may cause pulmonary damage.  

3) “CB2 was expressed more in the synovial tissues from the rheumatoid joints than in those from the osteoarthritis (OA) joints.” So these effects may be less likely in OA.

4) See #marijuana side effects


Il y avait chez Constance Synovie une particularité physiologique pour le moins surprenante. Ses genoux craquaient à chacun de ses mouvements. Constance tournait la tête et ses genoux grinçaient ; Constance faisait un signe de la main et ses genoux cliquetaient ; Constance clignait des yeux et ses genoux geignaient.

Cela ne gênait pas la jeune femme, ne l'empêchait pas de dormir, et  pour tout dire, elle ne s'en souciait guère. Bien sûr, sa vie sociale en fut contrariée. Jamais elle ne trouva de compagnon en mesure de supporter ces cliquetis permanents. Des amants, elle en eut, certains s'amusèrent un temps de cette singularité, mais tous se lassèrent rapidement. Difficile de dormir correctement quand vos nuits sont bercées par le tic-tac d'un métronome déréglé. Constance Synovie avait sagement choisi de travailler seule. Son atelier de couture-mercerie, « Constance Couture en Cas de Coup Dur » , acquit, en un rien de temps, très bonne réputation. Et bientôt l'on vint de loin pour solliciter ses talents de couturières.

Enfilant ses bottines, Igor Kakavinskipovich fit cette remarque à lui même : « Toutes mes chaussettes sont trouées… ». Le fameux compositeur russe était venu chercher l'inspiration qui lui faisait défaut dans le petit village de montagne où Constance Synovie naquit et où la craquante mercière vivait encore. Kakavinskipovich, lors de sa promenade quotidienne, n'avait pas manqué de remarquer la mercerie de mademoiselle Synovie, le nom de la boutique n'étant pas sans originalité. Aussi décida-t-il d'y apporter ses chaussettes à repriser.

Sur la route le menant vers « Constance Couture en Cas de Coup Dur », Igor Kakavinskipovich ruminait, désorienté par le manque d'imagination qui s'était emparé de lui depuis quelques temps déjà. Il espérait retrouver sa muse dans le paysage montagneux qu'il contemplait chaque matin, depuis la fenêtre de sa chambre d'hôtel. Mais jusqu'ici, il ne l'avait pas trouvée. Vide, incapable de penser, paralysé, engourdi et groggy comme un patient émergeant d'une anesthésie générale, le compositeur russe était désemparé. Lui qui ambitionnait d'inventer la musique du futur voyait son avenir se noircir, son cerveau ankylosé par le poids du néant. « Espèce d'ahuri, tu n'as plus d'autre idée que celle de faire raccommoder tes chaussettes… » bougonna-t-il.

Le tintinnabulement de la clochette signala l'entrée d’ Igor Kakavinskipovich dans l'atelier de la couturière. Le compositeur souleva son chapeau et salua la jeune femme. Il lui faisait part de son soucis de chaussettes quand il remarqua les cliquetis arythmiques provoqués par le genoux de la mercière. Vidant le sac sur sa table de travail, Constance commenta : « Il y en a des chaussettes ! j'espère que vous n’êtes pas  press… » D'un geste brusque, Kakavinskipovich mis son doigt sur la bouche pour faire taire la jeune femme. Non, il n'était plus pressé, l'inspiration s'était emparée de lui. Un maillage secret, une kabbale ésotérique semblait structurer les craquements répétés des articulations de Constance Synovie. Le compositeur resta bouche bée, les yeux écarquillés, abasourdi par la symphonie, articulée autour des crépitements irréguliers sonnés par les genoux de la mercière. « Puis-je rester le temps que vous reprisiez mes chaussettes ? » demanda hâtivement le russe, qui avait peine à cacher son ébullition. Constance acquiesça et l'homme s'assit, sortant de sa sacoche le papier à musique dont il ne se dépareillait jamais. Kakavinskipovich, euphorique, commença à couvrir ses feuilles de noires, blanches, croches et autres rondes avec une telle ardeur, que la couturière s'en trouva  à la fois amusée et fascinée. Le compositeur griffonna pendant des heures, lui seul entrevoyant le dessein caché derrière la métrique insinuée par les articulations croquantes de Constance Synovie.

Subitement, Igor Kakavinskipovich posa son crayon, se renversa sur sa chaise, jeta un regard hébété à la couturière et se fendit d'un rire tonitruant qui fit sursauter la jeune femme. Après avoir repris progressivement son souffle et essuyé la sueur qui avait perlé sur son front, il lança un regard profond vers Constance Synovie et lui déclara, sincère et solennel  : « Mademoiselle, vous êtes la plus belle chose qui me soit arrivée, épousez-moi, je vous en prie… ».  

Crack Your Knuckles?

How many times have you heard that “cracking” your knuckles is bad for you? At least that’s what your mother always told you. And isn’t that popping sound that occurs during a chiropractic adjustment the same thing?

Well, the answers are no and yes. No, mom is usually right but not always (sorry mom) especially about the cracking knuckles.  And yes regarding that popping sound that occurs during…

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Steve Coleman, Synovial Joints
Two years ago, I hailed Steve Coleman’s Functional Arrhythmias as a career breakthrough. His new CD, Synovial Joints (on the Pi Recordings label), is his masterpiece—a thrilling kaleidoscope, densely polyrhythmic, but also brisk and airy: music for serious listening as well as dancing in your head and on your feet.

Sun, 05/03/2015

via Home Theater Buzz