Compression stockings are socks that apply pressure to your legs in a very specific way to enhance the flow of blood. Compression is greatest at the ankle, and gradually decreases in strength as the stocking goes up the leg. This is called “graduated” compression and it is essential for medical efficacy. By squeezing your legs in this graduated manner, compression stockings help the valves in your veins open and close properly. This is essential to healthy circulation and enables your body to pump blood, against gravity, back up the leg and to your heart.
The amount or strength of compression is measured in millimeters of mercury (mmHg). Think how mercury is used in a thermometer. The mercury expands in precise relationship to your body’s temperature. While measuring the pressure of stockings is slightly different, the principle is the same.
A 20-30mmHg compression stocking has 20-30mmHg of compression at the ankle, and it gradually decreases toward the top of the stocking. Other standard levels of compression are 8-15mmHg, 15-20mmHg, 30-40mmHg and 40-50mmHg. The higher the numbers, the greater the compression. Most compression stockings do not have compression in the foot.
Graduated compression hosiery is considered a medical device and as such requires precision manufacturing and testing. These are images of three different pieces of testing equipment used by the company that makes our Allegro brand of compression hosiery. The HATRA (left), MST Professional (center), and NAHM (right).
Compression hosiery manufacturers use these machines to constantly test their products to ensure that the stockings you purchase have specific compression at various points in the stocking, with the correct levels of graduation. Compression therapy was invented in Europe in the last century. The quality of the end product depends greatly on the quality of the knitting machine and the fibers being used. The best American manufacturers use the same machinery and techniques that have been the standard in Europe. We are very fortunate in the US because the manufacturing of compression stockings has, for the most part, not been outsourced. There are some Asian and South American products on the market, some of which are good, but much of which falls short of US and European standards. Recently we have seen some inexpensive Asian imports with “reverse” compression, tighter at the top and looser at the ankle. This will restrict circulation and potentially do more harm than good.