1. What is Arthritis?
Arthritis is inflammation of the joints ("arthro" means joint, "-itis" means inflammation) that is usually brought about by the loss of articular cartilage. There are two main types of arthritis. The first and more common type is osteoarthritis (OA), i.e., "wear-and-tear" arthritis. Those with old football injuries may have noticed one knee getting arthritis earlier than the other one. Of course, as we age, we can get osteoarthritis in multiple joints when they all start to wear out. The second main type of arthritis is inflammatory arthritis, e.g., rheumatoid arthritis (RA). This type of arthritis is usually systemic in nature, meaning that it affects the whole body. For instance, some of us may have grandmothers or aunts with RA, who have severe deformities of all of the finger joints. The final common pathway for both of these types of arthritis leads ultimately to joint destruction.
2. What is the Role of Cartilage?
There are two main types of cartilage--fibrocartilage and articular cartilage. Fibrocartilage is a tougher cartilage that makes up the outer ear and the tip of the nose. The knee meniscus and the shoulder labrum are also comprised of fibrocartilage. Articular cartilage covers the ends of the bones inside a joint, e.g., the smooth stuff on the end of a chicken bone. This is pretty amazing material. The amount of friction generated from articular cartilage sliding upon itself is up to 50x less than sliding an ice cube across a frozen pond. Imagine that! Articular cartilage also protects the underlying bone by distributing the load over a larger surface area. As arthritis progresses, the articular cartilage gets thinner and thinner, to the point where it becomes "bone-on-bone" arthritis.
3. Can't You Just Cut Out the Arthritis?
When articular cartilage has worn away, the underlying bone sees increased forces. As a result, the body reacts by trying to distribute the forces over a larger surface area. It does this by forming new bone, which we see as bone spurs. So in fact, bone spurs are the body's way of trying to compensate for cartilage loss. That's why you can't just go in there and cut out the arthritis. First of all, if you took out just the bone spurs, they would grow right back, because the bone is still seeing extra load. Secondly, since arthritis is the loss of cartilage, you can't take out something that's already gone. The only way to truly get rid of the arthritis is to take off the ends of the bones and cap them with metal, i.e., a joint replacement.
4. Why Does the Joint Swell?
Once the cartilage cells are injured, they release cytokines. This is turn causes an inflamed environment full of enzymes and other chemicals that further degrade the cartilage. As you can see, this becomes a vicious cycle, leading to a swollen joint. That's why anti-inflammatory medicines are one of the first-line treatments to help slow the progression of the disease. In addition, as arthritis advances, more and more bone spurs are formed. Part of what you see as joint swelling likely includes bone spur formation. This is what leads to "knobby knees." The spurs make the joint look larger.
5. How Do I Treat Arthritis?
Arthritis is treated both surgically and non-surgically. The conservative management of arthritis includes weight loss, physical therapy, braces and anti-inflammatory medications. It may also consist of injections. Usually, when these treatments fail, then you're looking at the surgical options, which may include arthroscopies, osteotomies or joint replacements.
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