"So, why does this feel so good on my knees?"
"Why does this work?"
"What's happening in my knees when I do this?"
These are commonly asked questions by people who first experience the wonder of Tailgaters. This is a very simple, seemingly too simple really, exercise performed on a special device called an NK Table. An NK Table is an very old tool in physical therapy dating back to the 1950s. It was invented as a strengthening device; one of the first knee extension machines. The machine
has two adjustable bars or resistance arms on each side. The intent of these arms was to restrict the range of motion of the exercise and to change the magnitude of force within the arc of motion. But, I found that if you placed your legs on top of the resistance arms and used a very light weight, the machine could help you swing your legs - kind of like sitting on the tailgate of a pick up truck and swinging your legs in the air. Hence, the name Tailgater. The top image to the right is NOT how we use it; the bottom image is how we use it. Notice that the leg is on of the resistance arm.
Tailgaters feel really good if you have osteoarthritis of the knee. In fact, we have some clients who just want to sit and swing their legs and if they had their way that's all they would do. So, it's natural to wonder why something so simple can be so helpful.
First of all, the idea that easy motion on arthritic joints is helpful is not new. In the 70's, Robert Salter, MD invented the Continuous Passive Motion (CPM) device which helped patients move their knees after surgery. He found in his research that injured joints healed faster and more completely if they were moved gently. Of course, at the time, his colleagues all thought he was nuts. They were placing people in casts thinking that injured joints had to be protected. Well, it turns out that both camps were right. Diseased or injured joints need motion but the load that accompanies that motion must be light - at least at first. Salter's machine drastically reduced the load on the joint while it moved the joint and not it's the gold standard for procedures like Knee Replacement and ACL
Reconstruction.
In the 80's, I started studying the effects of exercise on joints and stumbled onto Salter's work (remember, no Internet then. It was all old school - go to the library!). I had been introduced to the NK Table at a hospital on one of my clinical rotations. So, what happened is like that commercial for Reese's Peanut Butter Cups where the two trucks collide, one chocolate and one peanut butter and bingo, you have the Reese's Peanut Butter Cup. Make the NK a CPM. Just change how you use the resistance arms. Make them assistance arms.
The science behind the light repetitive motion produced by a Tailgater exercise is this: light repetitive motion alters the secretion of a joint lubricant called hyaluronan*. This substance improves the fluid in your joint, makes it easier to move and it also binds water making your cartilage stiffer; more resistance to load. The result is that your knee feels better. It's not permanent though. You'll notice improvements almost immediately but you'll have to repeat the exercise frequently to reproduce the effect. Over time, you'll have to do less of it but most people would really rather do more; not less.
There are a few other ways to create light, repetitive motion in your knee:
- Use a skateboard. Sit down in a chair. Place your foot on the skateboard. Slide your foot back and forth.
- Use a furniture mover. These work best on carpeted surfaces. Do the same thing as with the skateboard.
- Use a rocking chair (yikes!). Yep. Rocking chairs create small, light motions in the hip, knee and spine. They really work.
- Swing your legs in water while sitting on the edge of a pool. For this to work, you have to swing your legs very slowly. Otherwise, you'll fatigue the muscles too fast.
People often ask if they can use cycling as a way to improve their joint health and the answer is, it depends. It depends on how much motion you have in your knee, how irritable your knee is, and how easily you can control the resistance on the bike. Cycling can create body weight or higher loads on your knee so it's usually not my first choice. But, it is an option. And, only on a stationary bike.
We suggest fifteen minutes per session and aim for three sessions per day. The key is to move slowly and feel very little fatigue in the muscles. The purpose is not to strengthen your muscles; it's to improve the fluid in your knee.
More motion; less load and your knees will feel better.
DK
*Ingram, K. R., A. K. Wann, et al. (2008). "Cyclic movement stimulates hyaluronan secretion into the synovial cavity of rabbit joints." J Physiol 586(6): 1715-29.
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