An article in the British Medical Journal found exercise as effective as arthroscopic surgery for repair of a torn meniscus. Article here. Actually, exercise is probably a lot more effective, since someone that does knee exercises will likely keep it up, thus maintaining knee health long-term.

How does exercise stimulate joint repair?

Let’s dissect the knee joint, since it is a notorious troublemaker.

The ends of the bones that meet to form the knee are covered with a thick, smooth, tough protective layer called the articular cartilage. You have seen this on the ends of chicken bones. It doesn’t look like the rest of the bone, being shiny, hard, smooth and white. The articular cartilage is manufactured by a cell type called chondrocytes, which originate within the bone.

The articular cartilage on these bones is around an eighth of an inch thick. The chondrocyte cells that manufacture it migrate from the bone to the surface, building and rebuilding the tough, smooth collagen layer. The cells on the outermost layer are squashed flat by the joint pressure. As they wear, they are replaced by those below. The middle part of the articular cartilage is somewhat rubbery, which absorbs shock and helps spread the load. The layer next to the bone is a tough layer resistant to compression.

The articular cartilages in a knee joint has tough a pad inserted between, called the meniscus, which further helps distribute the load. The meniscus can tear, but being composed chondrocyte-like cells, it can also repair.

Cells in the joints get no blood supply

The joint is then enclosed in a flexible sort of pouch called the synovial cavity. The wall of the pouch is made up of two types of cells, one of which secretes thick lubricating fluid, which fills the cavity. The well-lubricated articular cartilages can now slide against one another and against the meniscus. The synovial cavity is sometimes called the joint cavity. Surrounding the joint and the joint cavity is a system of ligaments that holds everything together.

The chondrocyte cells in the cartilage and the meniscus, though living, have no blood supply. How is this going to work? The solution is a little strange. It turns out that they get their nutrition straight from the synovial fluid. The cells that make up the synovial pouch wall do get blood, and release nutrients right into the synovial fluid. Making sure this fluid is made available to the cartilage-growing and meniscus-growing chondrocytes is the key to joint health. The joints get no nutrients from the bone itself.

Even though the synovial fluid provides nutrients, there is no oxygen available, so the chondrocyte cells have to generate energy solely from fermentation. This is a lot less efficient.

Don’t starve your joints

This feeding system for the articular and meniscal cartilage is a weak link. If the joints are immobile, hardly any of the nourishing synovial fluid gets distributed, things just sit, and the articular cartilage and meniscus begin to starve and don’t repair. Armed with this knowledge, it is easy to devise exercises that will repair joints and keep them in good shape. Two attributes are needed:

The joint needs to go through its full range of motion. This spreads the synovial fluid all about, and spreads the wear as well. Limited ranges of motion will cause certain points to wear out quickly, while surrounding regions may degenerate from lack of nutrient.

The thick fluid in the synovial cavity needs to be compressed and released. This forces synovial fluid into the articular cartilage where it can lubricate and nourish. This is akin to squeezing a wet sponge.

Exercises that embody the two of these will generally prevent osteoarthritis and accelerate healing. It helps to actually visualize the joint that is getting exercised. Is it getting compressed and released? Is it full range? Getting a full range of motion in everyday life is equally important. Walking, standing up, climbing stairs, etc.