How often do you hear people say "I would love to exercise but my knees just won't let me"? Indeed, knee problems occur commonly, whether you work out two hours per day or get your only exercise moving from the couch to the refrigerator. Keeping knees from injury requires a balance of power and strength in the different thigh muscles. This means not letting one muscle group become weaker than an opposing one.
Why Knee Injuries Occur
Repeating the same type of exercise every day will work one muscle group more than another, placing strain on the knee joint and supporting cartilage. For example, running works the quadriceps, the muscles group at the front of your thigh, far more than it works the hamstrings in the back of the thigh. This muscular imbalance may cause the kneecap to be thrown out of place, resulting in knee pain.
Knee pain can be caused by many conditions. Some, such as rheumatoid arthritis, cannot be prevented. Knee pain that is caused or made worse by physical activity can be improved with muscle toning and strengthening.
Two examples of knee pain directly related to exercise injury are runner's knee and ligament tear.
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Runner's Knee (Chondromalacia Patella)
Runners frequently develop knee pain caused by chondromalacia patella, a fancy name for anterior (front of the) knee syndrome. Ideally the kneecap (patella) rides up and down in a V-shaped groove on the thigh bone (femur) during walking, running or cycling. The kneecap can be thrown off track if your foot rolls in (called pronation) as you move from heel-strike to toe-off.
Many people pronate their feet when they walk, which is exaggerated with bigger strides during a run. If the kneecap is constantly thrown off track, the patella doesn't smoothly glide over the femur. Instead, the lining of cartilage underneath the patella scrapes against the thigh bone cartilage just below it. The irritated cartilage weeps fluid, yielding a swollen or stiff, painful knee.
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A much more serious injury is a tear of the anterior cruciate ligament (ACL). Ligaments are like cables that keep the bones together. When the cable pops, a big injury can occur. Any activity that involves jumping, sudden stops and starts, and rapid pivots can rip the knee ligaments.
Interestingly, women suffer ACL tears five to six times more than their male counterparts. Why are women so prone to ACL tears? It is possible that a woman's relatively wide hips put extra stress on her joints, and female hormones may weaken ligaments.
Is biology destiny? A woman may not be able to change her anatomy or hormones, but other factors for knee injuries are within her control. For example, stretching exercises to improve knee flexibility, weight-lifting activities to strengthen thigh muscles, and recurrent jumps with flexed knees for knee-injury prevention, dramatically reduce knee injuries during a season of play.
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Preventing Sports-Related Knee Injury
By making strong quadriceps and hamstrings your allies, you can prevent knee pain and protect your knees from injury.
To help prevent sports-related knee injures:
- Avoid drastic changes in your exercise program. Adjust the exercise regimen by one variable at a time. For example, don't increase the number of repetitions and increase weights at the same time.
- Walk or run on cushioned surface or ground rather than concrete.
- Make sure shoes fit well and are not worn out.
- Choose the appropriate shoe for the fitness activity. For example, running shoes are not designed for pivots and turns, but tennis and racquetball shoes are designed for sudden stops and starts.
- Warm up and cool down with each activity. Gentleness is key. Avoid bouncing, jerking or forcing the legs into different positions. Include stretching before and after the activity.
- Avoid excess weight. Extra pounds place added stress on your knees.
- Consider avoiding activities such as basketball and soccer if you have a knee problem, because sudden twists and turns may knock out your knees.
- If you already have a knee problem, apply ice to the knee before and after your workout to reduce swelling and stiffness.
- Try orthotics (supportive shoe inserts) to improve your foot mechanics by preventing foot rolling and excessive knee motion.
- Work on your balance. Balance and stability training helps the muscles around your knees to work together more effectively to brace and support your knees.
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Don't let your knees become your weakest link. No matter how fit and balanced you are, there is only so much torque a knee can handle. With proper training, conditioning and stretching, you can help prevent knee injury and damage, and lead an active, healthy lifestyle.
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Paulette Chandler, M.D., M.P.H., is a clinical instructor of medicine at Harvard Medical School and an attending physician at Brigham and Women's Hospital.