The knee is a synovial joint consisting of the articulation between the femur and tibia bones. Known medically as the tibiofemoral joint, the knee is controlled by numerous muscles and supported by ligaments. The knee joint is prone to injury as it is subjected to a high degree of physical stress during day-to-day activities and sports.
Anatomy of the Knee Joint
The knee is capable of extension, flexion and a small degree of rotation. The muscles that extend the knee are the quadriceps located on the front of your thigh: rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. The hamstring muscles on the rear of your thigh flex your knee and these are called biceps femoris, semitendinosus and semi membranosus. Your knee can also rotate slightly when bent. This action is controlled by the gracilis and sartorius muscles. To keep your knees in good health and minimize your risk of injury, all of these muscles should be kept strong and flexible.
Common Knee Injuries
A large number of conditions that can affect your knees. The tendon that connects your quadriceps muscles to your tibia can become inflamed in a condition called patella tendonitis. This is commonly caused by explosive activities such as jumping and sprinting. Illiotibial band syndrome is a condition where the muscles and connective tissue at the side of the knee become tight and inflamed resulting in pain. This condition is often made worse by running long distances downhill. Because the knee is a major weight-bearing joint it is also prone to osteoarthritis --- a condition of wear and tear to the articular surfaces. Osteoarthritis is more common in the elderly, but can also be the result of playing lots of sports.
Exercises to Avoid
Some exercises are beneficial for your knees while others may cause damage, either at the time of exercising or as a result of long-term exposure. Very deep squats place a great deal of strain on the patella tendon at the front of the knee. Performing leg presses where the knee is bent beyond 90 degrees also stresses the patellar tendon. Both deep squats and leg presses are best avoided for knee health. Heavy leg extensions create a shearing force between your femur and tibia, which can be very stressful for the ligaments that support the knee including the anterior and posterior cruciate ligaments.
Beneficial Exercises
Exercises that enhance knee health include leg presses and squats up to 90 degrees of knee flexion, lunges, step ups and dead lifts. Exercises that use unstable surfaces to challenge your balance are also beneficial. These include performing squats using a wobble board and balancing on one leg. One-legged exercises are especially beneficial if you play sports. Most sports involve single leg ground reactive movements such as running, sprinting and rapidly changing direction, all of which place a lot of stress on your knee joints.
Considerations
Knee pain can often be the result of muscle strength or flexibility imbalances between posterior and anterior muscle groups. Keeping both your quadriceps and hamstrings balanced helps ensure that you will not place uneven stresses on your knees. Some knee pain can be caused by more serious physical problems such as floating bodies within the joint space, damage to the articular surface or injury to any of the ligaments that stabilize the knee. If you experience knee pain you should have it diagnosed by a medical professional to ensure that any exercises you perform will not make the condition worse. While exercise is generally good for your knees, some injuries may be made worse by the wrong kind of workout.
References
- Sports Injury Clinic: Anatomy of the Knee
- "Sports Injuries: Their Prevention and Treatment, Third Edition"; Per Renstrom Ph.D, M.D.; 2007
- "Anatomy of Exercise: A Trainer's Inside Guide to Your Workout" Pat Manocchia; 2009
