Joints can handle some heavy pressure. For example, knees have to handle a force of three to four times a person’s total body weight on average when just talking a walk. The force of a deep knee bend during a squat can increase to nine times the body’s weight. So just imagine multiplying weight of more than 150 pounds times a minimum of three or four, and then even more. That can add up to a lot of heavy work on knee joints over a period of time.

Now for the science behind this scenario. The place where two bones meet is called the joint- the bone ends are covered with cartilage, also known as gristle.

This cartilage is sturdy, elastic, spongy and compressible, and keeps the bones from rubbing against each other at the joint. The cells of this cartilage, called chondrocytes, are thought to be the longest living cells of the body. Surrounding the bones and cartilage is strong, fibrous capsule lined with synovium, a thin membrane that lubricates the joint area with fluid. The end result is less friction or smoother rubbing together of the bones. This fluid also feeds the cartilage cells, keeping them healthy, and is “pumped” into them during joint movement. Thus lack of movement (activity / exercise) can be unhealthy.

Other parts of the body involved with this arthritic scenario include muscles, tendons, ligaments, bursea and mental activity. Muscles, attached to bones with tendons and ligaments, move bones by contracting. They also cushion movement, absorbing impact or shock. Throughout the muscle and tendon areas are bursae or sacs filled with fluid. These also help cushion movement. And all the coordination of these parts during movement, are controlled by the brain. The brain communicates via nerves throughout the body, in particular the muscles, to prepare joints for activity.

The exact science of what actually causes arthritis is still being researched. For most of the 100-plus forms of arthritis, the causes are unknown. Injury, overuse of joints and mechanical issues with joints (such as skeletal abnormalities, worn out joint muscles etc) can lead to arthritis. Issues relating to bacteria and germs are also thought to have some link to arthritis. Heredity, stress, drugs, food allergies and viruses have also been linked to some forms of arthritis, as have diet, poor circulation and lack of movement.

Arthritic joints can be affected with inflammation when bacteria or a virus (or other undesirable element) enters the joint area or when an injury occurs. When foreign matter enters this area, or the area sustains injury, white blood cells, antibodies and other natural “fighting” mechanisms automatically kick in internally to help. These fighters cause swelling, redness and heat as the body fluid moves around. The symptoms of this inflammation, one of the uncomfortable issues associated with arthritis, are redness, swelling and tender joints.

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