This his the case of your knee joint, hip joint, shoulder joint, elbow joint, wrist joint and more.
Its particularity is to be enveloped in a synovial capsule, on the inside there is a synovial membrane that produces synovial fluid. The synovial capsule envelopes as well the ending part of the bones coming together at the joint and, of course, these bone endings are usually covered by a smooth surface called cartilage.
Cartilage and synovial fluid are here to make the movement between your bones smooth, easy, soft and sustainable… can you imagine a joint where 2 bones come in direct contact and rasp each other every time you bend your elbow? Well, it can happen… it’s the case of degenerative joint diseases as arthritis or osteoarthritis, enough common in modern days over a certain age but not only.
Beside being a lubricant for the joint the synovial fluid has other functions: it’s a shock absorber and a nutrient/waste transporter inside the joint helping cartilage and bone to stay healthy.
I give you a couple of links:
http://www.med.umich.edu/lrc/coursepages/m1/anatomy2010/html/modules/joints_module/joints_01.html
http://www.nhs.uk/Conditions/Osteoarthritis/Pages/Introduction.aspx
In the first you can go a little deeper in your anatomical knowledge of joints, the second is about one of the typical and potentially common joint disease we mentioned before.
Now let’s go straight to the next post, it will be about the effects of yoga on your joints!