Why Movement Saves Joints

Movement is the lifeblood of joints.

To understand why movement is so critical to maintaining your joints in a healthy state, we need to look at what happens when the joint movement is restricted. One way scientists have studied this is to look at what happens when they artificially immobilize the joints.

In one attempt to study what happens to immobilized joints, doctors at University College London completely prevented movement in the hind hock joints of sheep for 12 weeks. In this study, they restricted movement of the joint, but not of the entire leg. This ensured that they were not going to measure decreased blood circulation to the entire leg as a possible effect. The doctors were looking for a specific substance called hyaluronic acid (HA), which is one of the most critical molecules for maintaining the lubricating ability of joints.

When joints were immobilized, hyaluronic acid levels fell to a surprising 0.68 mg/ml in the joint fluid. This was compared to 1.68 mg/ml in the joint fluid of joints that were not immobilized. Translation: failure to move the joints caused levels of the lubricating fluid (hyaluronic acid) to fall by more than 50 percent.

This is really quite important to understand. Doctors are trying to find ways to deliver hyaluronic acid to the joints to improve lubrication. Injection directly into the joints is one method, but it is usually reserved for more severe cases of OA. Oral supplementation with HA is another method that is gaining some promise and it is being used in a variety of supplements with varying results. While helpful, none of these are as valuable as stimulating the natural production of HA through movement.

Doctors have been impressed by the growing evidence for movement benefits, but some recent work at Howard Hughes Medical Institute adds new weight to the idea. They showed that continued passive movement cause the cartilage cells (called chondrocytes) to produce vastly more proteoglycan 4. In their study, 40 percent of the cartilage cells in one large surface region of continuously sliding cartilage produced PG-4, compared with only 13 percent of the chondrocytes in immobilized joints. Proteoglycan 4 is another important lubricant in joints. This clear finding that movement stimulated the release of more PG-4 adds strength to the argument that we must move our joints in order to maintain joint health.

So, if not using a joint leads to a decrease in the joints most crucial lubricants, what happens when the joint is being deliberately moved, exercised, or used? In 2008, this was tested directly in rabbits. These doctors at the University of London found that “Cyclic joint movement approximately doubled the net hyaluronic acid secretion rate.” They went on to write that “The results demonstrate for the first time that the active secretion of HA is coupled to joint usage.”

From these studies, it appears that:

1) Immobilized joints produce less hyaluronic acid, (less lubricant)

2) Actively moving joints produce more hyaluronic acid (more lubricant)

At the risk of using a cliché, the old adage of use it or lose could be the central message of keeping your joints healthy for as long as possible. Further evidence of this comes with the study at the University of Osaka Medical School. Seventeen people with knee osteoarthritis were asked to perform isometric exercises of the quadriceps (the large thigh muscle) for a period of 3 months. Not only did pain scores improve, but the viscosity of joint fluid also improved. These doctors found that isometric exercise of the quadriceps led to:

Decreased pain
Beneficial increase in joint fluid viscosity (from 45.8 to 59.8 mPas)
Increased molecular weight of hyaluronic acid in the joint

The doctors remarked, “Isometric quadriceps exercise resulted in significant changes in joint fluid biochemical parameters, and these changes, at least in part, may explain the ameliorative [beneficial] effect of muscle exercise for osteoarthritis of the knee.”

Increased hyaluronic acid synthesis in joints through movement may even confer another benefit. In a recent study published in the journal Pain, increased hyaluronic acid concentration apparently lessened the pain signals associated with the nerves traveling from the joint to the spinal cord. This could mean that increasing joint HA levels through movement could also lessen pain by direct biochemical means.

While there is much to say about movement, joint fluid, and joint pain, it is becoming clear that the following is true:

Not using a joint probably reduces the levels of hyaluronic acid and other important lubricating fluids within the joint.
This loss of HA over time leads to increased joint destruction and pain.
Movement and exercise improve HA levels in the joint, improve mobility, and reduce pain.

Having highlighted the benefits of movement to increasing the lubricating substances in joints, we have to address one more item. That is, can additional benefit be gained by going beyond movement and into actual strength training? The answer appears to be that strength training does confer additional benefits. In a recent study at Purdue University, people with OA who used strength training experienced less narrowing of the joint space of the knee over a 30 month period than those who just used range of motion exercises. Joint space narrowing (on x-ray) would be one measure indicating that cartilage in the joint is being reduced.

[Pitsillides, AA, Skerry, TM, Edwards, JCW. Joint immobilization reduces synovial fluid hyaluronan concentration and is accompanied by changes in the synovial intimal cell populations. Rheumatology 1999;38:1108-1112.]

[Ingram, KR, Wann, AK, Angel, CK, et al. Cyclic movement stimulates hyaluronan secretion into the synovial cavity of rabbit joints. J Physiol 2008;586(6):1715-29.]

[Myaguchi, M Kobayashi, A, Kadoya, Y, et al. Osteoarthr Cart 2003;11(4):252-9.]

[Gomis, A, Miralles, A, Schmidt, RF, Belmonte, C. Nociceptive activity in an experimental model of knee joint osteoarthritis of the guinea pig: Effect of intra-articular hyaluronan application. Pain 2007;130(1-2):126-36.]

[Mikesky, AE, Mazzuca, SA, Brandt, KD, et al. Effects of strength training on the incidence and progression of knee osteoarthritis. Arthr Rheum 2006;55(5):690-9.]

Movement as Good as Injectable Hyaluronic Acid?

The three main ways to increase hyaluronic acid in joints are:

Hyaluronic acid injection directly into the joint
Taking hylauronic acid tablets by mouth
Exercise

Injection of hyaluronic acid into arthritic joints is becoming increasingly common. There are several benefits to this, but the success is somewhat dependent upon which form of HA is used in the injection. Doctors have recently attempted to compare the success of injections of HA to exercise and movement. The first of these studies was published in 2006, where doctors found that the benefits of exercise were comparable to that of HA injections. This study of 200 people showed that both treatments caused improvement in people with arthritis of the knee. This is really quite interesting to consider--that movement or exercise was as beneficial as injections of joint lubricating fluid.

In 2008, a similar study was reported, this one studying people with arthritis of the ankle. Once again, they compared exercise to injections of hyaluronic acid into the ankle joint. Both groups improved to a similar extent.

These types of studies are giving us more confidence to say that movement can preserve joints. As noted above, movement is the lifeblood of joints.

[Karatosun, V, Unver, B, Ozden, A, et al. Intra-articular hyaluronic acid compared to exercise therapy in osteoarthritis of the ankle. A prospective randomized trial with long-term follow-up. Clin Exp Rheumatol 2008;26(2):288-94.]

[Karatosun, V, Unver, B, Gocen, Z, et al. Intra-articular hyaluranic acid compared with progressive knee exercises in osteoarthritis of the knee: a prospective randomized trial with long-term follow-up. Rheumatol Int 2006;26(4):277-84.]

If you understand a bit about two tissues within joints, you can do a lot to take care of your joints. These two tissues are:

Cartilage
Synovial fluid

Synovial fluid

Synovial fluid is the slippery stuff that fills up the joint space. It is also found in the cartilage. The material that creates viscosity is hyaluronic acid. Hyaluronic acid lowers the viscosity of the very watery synovial (or joint) fluid. This compound is also important to know about because it is now being used in treatment of arthritis and to support healthy joints. The other important compound is called lubricin, which provides the lubrication to cartilage. Doctors are actively searching for natural compounds that stimulate lubricin production.

Cartilage is a strange material, different than almost all other tissue. It is very long-lived, meaning it does not turn over like other tissues. Also, cartilage does not have blood vessels like other tissue. Cartilage relies on the blood supply of the underlying bone. Then through a process called imbibition, the cartilage has to “pump” the nutrients into itself through movement. You can view this as a sponge in a tiny amount of water. If you were to repeatedly push down on then lift up on the sponge, the water would go in and out.

This is how cartilage takes in its nutrients. In the case of our joint cartilage, the “pumping” action takes place through our movement. Thus, walking, running, jumping, and other activities repeatedly press and release the cartilage, which pumps the blood supply (and nutrients) in and out. This is what keeps cartilage alive.

Therefore, movement is the lifeblood of cartilage. Even though your impulse may be to be inactive when you have joint pain, you must understand that being inactive starves the cartilage of its lifeblood.

So, movement can save your joints. Now, if you couple an anti-inflammatory diet and joint supportive nutrients with movement (increased activity), you significantly increase your chance of keeping joint tissue healthy.