The system most affected by osteoarthritis is your joints. Put simply, a joint is where two separate bones are connected, allowing you range of motion and flexibility in your body [source: NIAMS]. Almost all joints in your body can be affected by osteoarthritis; however, osteoarthritis is most likely to occur in your hands, knees, hips, neck and lower back. Osteoarthritis, also known as degenerative joint disease, occurs when the cartilage in your joints deteriorates due to many years of wear and tear [source: Mayo Clinic].
Moveable joints are rather complex and are composed of many intricate parts. Cartilage is the most important joint component when we look at the symptoms of osteoarthritis. Cartilage is a smooth coating found on the tip of bones, which is made primarily of water. Cartilage is also composed of collagen, proteoglycans and chondrocytes [source: NIAMS]. Collagen is the basis for many different organs in the body, including your skin, and it is composed of fibrous proteins [source: NIAMS]. Proteoglycans are composed of protein and sugars. Proteoglycans and collagen bind together and form a web of tissue, which is flexible and absorbs shock, an essential component for a healthy joint. Finally, healthy chondrocytes help build collagen [source: NIAMS].
The other components of a joint include the joint capsule, the synovium, synovial fluid, ligaments, tendons and muscles. The joint capsule keeps everything together in a protective membrane. The synovium is a membrane that secretes synovial fluid in the joint; the fluid lubricates the joint and helps keep the collagen smooth. Finally, ligaments, tendons and muscles surround the joint and provide the joint with strength and flexibility of movement. In an unhealthy joint, the cartilage is weak, bone spurs are produced and synovial fluid increases [source: NIAMS]. Once a joint loses it's cartilage, bones begin to rub together. Ultimately, these changes in physiology result in joint pain, swelling and stiffness [source: Mayo Clinic].