The quadriceps are a large group of muscles located on the front of the thighs. They are a powerful knee extensor used in climbing, jumping and rising from a seated position. In her book "Anatomy and Physiology," Elaine Marieb notes that the tone of the quadriceps plays an important role in strengthening the knee joint. When these muscles begin to atrophy, or decrease in size, problems in the knee joint may arise.
Muscle atrophy is defined as the wasting or loss of muscle mass. A decrease in muscle strength accompanies this decrease is muscle size. Muscle atrophy results in decrease muscle tone, which is the low levels of contractile activity in relaxed muscles that keep the muscles healthy and ready to react to stimulation. Adequate quadriceps muscle tone is extremely important in reinforcing the knee joints.
Atrophy of the quadriceps muscles can occur for a variety of reasons, one of which is lack of activity or exercise of the muscles. Individuals who work at sedentary jobs, wear a leg cast or brace that prevents movement in the knee joint or are bedridden are at very high risk for atrophy of the quadriceps. Those who suffer from medical conditions such as stroke and arthritis and have limited mobility may also experience muscle wasting. Injury or disease of the femoral nerve, the nerve that innervates the quadriceps, results in a more severe type of atrophy. Lastly, sarcopenia, the loss of muscle mass associated with aging, is another common cause of quadriceps muscle atrophy.
The consequences of muscle atrophy in the quadriceps go far beyond a decrease in muscle strength. Decreased muscle tone and strength of your quadriceps could increase your risk for developing arthritis or intensify the severity of already existing arthritis in your knee. Strong quads will support your knee while absorbing some of the impact your joint must endure. American Family Physician notes that weakness of the quadriceps muscles is the most often cited area of concern when dealing with patellofemoral pain syndrome, a disorder characterized by anterior knee pain. In this instance, toned quads will keep your knee cap tracking in its proper position and will reduce wear of the patellar cartilage. The worst consequence of quadriceps muscle atrophy would be complete disability of your leg.
Although it is never too late to begin a quadriceps-strengthening program, prevention of any muscle atrophy to begin with is key. If you work a sedentary job, make sure to get up and move around several times a day. Take the stairs instead of the elevator to really get a quad workout it. For those who are incapacitated due to injury, obviously you will have to endure some level of atrophy. In this case, rehabilitation is crucial -- begin with gentle stretching and strengthening exercises and progress as instructed by your doctor. The best way to prevent muscle atrophy is to build and maintain strong quadriceps. This can be accomplished through regular aerobic and strength-training exercises. Some quad-targeting exercises include running, stair-climbing, squats, step-ups and lunges.
- "Physiology of Sport and Exercise, Third Edition"; Jack H. Wilmore, David L. Costill; 2004
- "Anatomy & Physiology, Second Edition"; Elaine N. Marieb; 2005
- MayoClinic.com: Arthritis
- "Journal of Applied Physiology": Muscle-Specific Atrophy of the Quadriceps Femoris With Aging
- American Family Physician: Patellofemoral Pain Syndrome: A Review and Guidelines for Treatment
- University of Maryland Medical Center: Muscle Atrophy - Overview