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7 Things You Didn't Know About Your Joints

Dr. Grant Cooper Apr 6th, 2012 (updated Jun 16th, 2015)
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Human joints are amazing structures, but they are also vulnerable to damage, inflammation and wear-and-tear. Find out more about your joints and how to protect them from arthritis.

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What is the difference between ligaments and tendons?
What is the difference between ligaments and tendons?

Ligaments are tough fibrous bands of tissue that attach bone to bone. Tendons are another kind of tough bands of tissue that attach muscle to bones.

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Cartilage is vital to joint health
Cartilage is vital to joint health

Healthy cartilage is vital for joint health.  Cartilage lubricates the joint and also provides important cushioning properties.

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Charged particles in your joints
Charged particles in your joints

Negatively charged particles resist being pushed together just as two similarly charged magnets resist being pushed together. The closer the magnets get together, the harder it is to force them closer. Because cartilage is filled with negatively charged chondroitin molecules, it resists being pushed together. This gives it its incredible cushioning powers!

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Cartilage and water
Cartilage and water

Cartilage is 80 percent water!  This provides the cushioning in a joint, providing protecting between the two bones.

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Bursae
Bursae

Bursae are small fluid-filled sacs found throughout the body. They cushion sensitive areas of the body (such as where certain bones protrude close to the skin surface and are susceptible to bruising). Unfortunately, sometimes bursae can become inflamed, resulting in “bursitis.” One of the more common causes is repetitive friction over a bursa, leading to irritation and, ultimately, inflammation.

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Blood supply to joints
Blood supply to joints

In fact, joints do not have a direct blood supply at all! Joints get banged around a lot and if they had a large blood supply, each time they were banged, bruised, or twisted, they could bleed. Recurring bleeding into the joint could lead to tough fibrous scar tissue developing inside the joint, which would inhibit functioning. So, instead, the joint capsule receives nutrients from and eliminates waste products to the blood. 

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Joints need to move
Joints need to move

If joints don’t move then the synovial fluid remains inside of the cartilage. If the synovial fluid remains inside the cartilage, it cannot interact with the joint capsule and so cannot exchange nutrients and waste with the joint capsule’s blood. When joints move, the synovial fluid is pushed out of the cartilage and the fluid can then exchange nutrients and waste products with the blood.