Joints are a part of our human anatomy. They refer to the areas in our body where bone ends meet. Without joints, we won’t be able to move.
Thus, most of us are keen on knowing why our joints tend to weaken over time and how we can take better care of them. But there’s definitely more to learn about our joints.
Our Joints are Also Full of Fun Facts that You May Not Have Known
The topic of “joints” is complex and vast – only medical specialists would be able to have comprehensive knowledge about the joints and bones. Hidden within such knowledge are fun facts about joints that most people wouldn’t know.
Here are 4 interesting facts that you may not have known about your joints.
Fact 1: There are immobile joints in our skull called “sutures”
Yes, you read that right – not all joints in our body are mobile. There are actually immobile joints in our skull. Being immobile makes sense considering our skull cannot bend, but why are there joints in our skull?
Contrary to popular belief, the human skull does not only comprise of one big bone. In fact, our skull is an intricately constructed structure comprising of 22 smaller bones¹. Connecting these smaller bones together are immobile joints called “sutures”, which appear on our skull as thin lines that look like cracks.
As babies, these sutures are somewhat separated and have not completely connected the skull bones together. This is to allow some space for the skull bones to expand as our brain grows larger in size. Naturally, as babies grow, the sutures start to “close” as the skull bones meet and start adhering to each other². The skull bones can adhere as there are dense, fibrous tissues at these sutures “gluing” our skull bones together.
Once all the skull bones have attached to form the skull, these sutures close and show up as thin lines on the skull. This is rather similar to a cracked egg shell that is still holding its shape, except that it's in the shape of a skull.
Thus, these sutures are immobile joints which play an important role in holding the skull bones together for a rigid skull structure.
Fact 2: Synovial joints ‘pop’ due to gas escaping from them
Movable joints such as those at our knees, elbows and hips are called synovial joints. These synovial joints have a thin layer of strong and smooth articular cartilage covering our bone ends. This cartilage helps to reduce friction between our bones, making movement smoother and easier³. This is further enhanced by a lubricating synovial fluid found in our synovial joints⁴.
The synovial fluid contains dissolved gasses, such as nitrogen and oxygen. When we move our joints, nitrogen gas bubbles can form in the synovial fluid, leading to a buildup of gas bubbles in our joints. These bubbles can eventually burst to release nitrogen gas during movement, causing those familiar joint popping sounds⁵.
The next time you crack your knuckles, you’ll know where those popping sounds come from.
Fact 3: Our main weight-bearing joints are the ankle, knee and hip joints
There are multiple joints in our body, but some joints do more work than others. Though there are other joints helping to share the load, it is our ankle, hip and knee joints that do most of the heavy-duty work by bearing our weight⁶.
These three important joints are what mainly holds us up whenever we stand and carry our body’s weight. In fact, for every extra kilogram, the knee joint is estimated to carry 2-3 times that amount due to the force exerted on our knee joints when we walk⁷. Our knee joints are indeed very strong and essential, allowing us to do this every day.
Of course, the greater the weight our joints carry, the faster they degrade. Thus, maintaining a healthy weight is beneficial to not just your overall health but also your weight bearing joints.
Fact 4: Women are more prone to joint problems than men
There are generally higher occurrences of women having Osteoarthritis (OA) compared to men⁸. In fact, 62% of patients with OA are women⁹. Though the exact cause is unknown, there are some reasons being hypothesized.
One of the main reasons is due to the differences in physiological makeup of both genders.
In general, women have thinner cartilage and smaller joint surfaces than men. This could be a reason for higher incidences of OA among women, as the thinner cartilage can lead to faster degradation¹⁰.
In addition, post-menopausal women experience a decrease in their level of estrogen, a female hormone that can help strengthen joints and reduce inflammation. Losing estrogen would thus bring about weaker joints and greater inflammation¹¹'¹². This is a natural part of being a woman as we age. Thus, taking good care of our joints becomes even more important.
There’s definitely more to our joints than just these few fun facts. After all, our joints are part of a complicated system running throughout our body that are necessary to hold us together and allow for movement. However, in our day-to-day lives, we often forget that these complicated joints are crucial in supporting every step and responsible for every movement we make. Take the time to appreciate your joints and maintain them well. Don’t take them for granted – do what you can to keep your joints happy and healthy.
Anderson, B.W. and Kharazi, A. (2019). Anatomy, Head and Neck, Skull. [online] Nih.gov. Available at: https://www.ncbi.nlm.nih.gov/books/NBK499834/.
www.urmc.rochester.edu. (n.d.). Anatomy of a Newborn Baby’s Skull - Health Encyclopedia - University of Rochester Medical Center. [online] Available at: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=90&contentid=p01840
Furmann, D., Nečas, D., Rebenda, D., Čípek, P., Vrbka, M., Křupka, I. and Hartl, M. (2020). The Effect of Synovial Fluid Composition, Speed and Load on Frictional Behaviour of Articular Cartilage. Materials, 13(6), p.1334.
Seidman, A.J. and Faten Limaiem (2019). Synovial Fluid Analysis. [online] Nih.gov. Available at: https://www.ncbi.nlm.nih.gov/books/NBK537114/.
Protopapas, M. and Cymet, T. (2002) Joint cracking and popping: understanding noises that accompany articular release. Journal of Osteopathic Medicine, Vol. 102 (Issue 5), pp. 283-287.
Seki, E., Matsushita, I., Sugiyama, E., Taki, H., Shinoda, K., Hounoki, H., Motomura, H. and Kimura, T. (2008). Radiographic progression in weight-bearing joints of patients with rheumatoid arthritis after TNF-blocking therapies. Clinical Rheumatology, 28(4), pp.453–460.
D’Lima, D.D., Fregly, B.J., Patil, S., Steklov, N. and Colwell, C.W. (2012). Knee joint forces: prediction, measurement, and significance. Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine, [online] 226(2), pp.95–102.
O’Connor, M.I. (2007). Sex differences in osteoarthritis of the hip and knee. The Journal of the American Academy of Orthopaedic Surgeons, [online] 15 Suppl 1, pp.S22-25.
Osteoarthritis Action Alliance. (n.d.). OA Prevalence and Burden. [online] Available at: https://oaaction.unc.edu/oa-module/oa-prevalence-and-burden/.
Otterness, I.G. and Eckstein, F. (2007). Women have thinner cartilage and smaller joint surfaces than men after adjustment for body height and weight. Osteoarthritis and Cartilage, 15(6), pp.666–672.
Roman-Blas, J.A., Castañeda, S., Largo, R. and Herrero-Beaumont, G. (2009). Osteoarthritis associated with estrogen deficiency. Arthritis Research & Therapy, [online] 11(5), p.241.
Chlebowski, R.T., Cirillo, D.J., Eaton, C.B., Stefanick, M.L., Pettinger, M., Carbone, L.D., Johnson, K.C., Simon, M.S., Woods, N.F. and Wactawski-Wende, J. (2013). Estrogen alone and joint symptoms in the Women’s Health Initiative randomized trial. Menopause, 20(6), pp.600–608.
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