Understanding cartilage increases awareness of its importance.
One of the most fascinating components of the human body is cartilage, an incredibly versatile material. Trying to describe cartilage is like the six blind men who try to figure out what an elephant is:
“The elephant is like a pillar,” said the man who touched his leg.
“Oh no! is it like a rope,” said the man who touched the tail.
“No, it is like a thick branch of a tree,” said the one who touched the trunk.
“It is not. It is like a big hand fan,” said the man who touched the ear.
“It is like a huge wall,” said the one who touched the side of the elephant.
“It is like a solid pipe,” said the man who touched the tusk.
So it is with cartilage. Is it like ice? A rubber cushion? A sponge? A shock absorber? Pushing two negative magnets together? A factory? The answer is, it’s like all of them.
Cartilage has a variety of properties that make it the perfect substance to facilitate joint movement and absorb shock. It is considered a connective tissue. Where the ends of two bones meet to form a joint, cartilage surrounds the ends, forming a smooth covering. This covering is slippery, like ice – up to eight times as slippery, depending on the type and location of the cartilage—which allows the bones to slide against each other as the joint moves.
Cartilage is made up of a matrix of fibrous protein strands called collagen. Collagen has compressive strength, meaning it can bear a pressure load but return to its size when the pressure eases, similar to heavy duty rubber. This helps protect bones when they are subjected to force; for example, the small joints called facet joints between each backbone (vertebra) that makes up the spinal column experience extra stress when you are carrying a very heavy object, so the cartilage surfaces where the small bones meet are compressed as if they were hard rubber pads cushioning them, but immediately return to normal when you set the object down.
In the protein matrix, there are very tiny cavities that store liquid (water and a special liquid called synovial fluid). If you’re relaxing on the couch watching TV, cartilage can be thought of as a damp sponge waiting to be used. A commercial comes on and you decide to get a glass of water. The act of standing up involves putting force on your knees and other joints. This force pushes synovial fluid and water out of the tiny cavities into other space in the joint, similar to squeezing the damp sponge. When you sit back down, the liquid returns to the cartilage cavities. This action is also similar to a shock absorber; when pressure is put on the piston inside the tube of oil, “the oil is forced through tiny holes and valves…precisely controlling the amount of movement.”i
There is another way in which cartilage protects joints and bones from being forced too closely together. If you have ever tried to push the negative ends of two bar magnets together, the closer they got the more resistance you felt, as if there were an invisible energy pushing them away from each other. According to Dr. Grant Cooper, cartilage is “filled with negatively charged chondroitin molecules. Negative particles resist touching each other with astounding atomic force. When the joint is made to bear weight, these chondroitin molecules are pushed together, but their negative charges resist.” iiIsn’t this amazing? Cartilage harnesses the properties of atoms to protect joints!
Finally, cartilage contains its own self-producing factory. Within the matrix formed of collagen strands and other types of protein, there are living cells called chondrocytes. In fact, these are the only cells in cartilage, while the rest is building materials and fluids. Chondrocytes have a particular job to do: they “manufacture” and maintain the cartilage matrix.
So now you see that cartilage is like ice, rubber, a sponge, a shock absorber, two negative magnets being pushed together, and a factory. Despite these qualities, cartilage is not impervious to harm. Over time, depending on many factors in a person’s lifestyle and health, cartilage is subject to deterioration. It can’t rebuild itself forever once it has worn away, which is called osteoarthritis.
If the facet joints in the spine become worn to the point where the space between the vertebrae is diminished – resulting in pressure on nerves – intense pain can result. Only a doctor can determine the source of back pain, which can be caused by many things, so a thorough evaluation is important. If it found that osteoarthritis of the facet joints is the problem, the Sperling Medical Group offers MRI-guided Focused Ultrasound (MRgFUS) to relieve pain.
Remember that “an ounce of prevention is worth a pound of cure.” Take good care of your wondrous cartilage by maintaining healthy weight and avoiding undue repetitive force on joints. Hopefully learning about cartilage and its many properties will contribute to treating it with respect. As Dr. Cooper points out, “Scientists have put men on the moon, eradicated polio, made flying an everyday event, and decoded DNA, but they haven’t yet been able to create a substance that is better suited for joints than the body’s own healthy cartilage.”iii
- Facet Pain