The position of your knees, about halfway between your ankles and hips, makes them vulnerable to injury. Preventing these injuries requires a proactive approach, which sometimes uses the exercises performed to treat existing injuries. The most effective workouts activate the muscles that support the movements of your knees, while stabilizing the joints that surround them.
Closed vs. Open Chain
During open-chain exercise, your feet move freely while the rest of your body remains stationary. In contrast, during closed-chain exercise, the feet stay in contact with the surface as the rest of your muscles perform the exercise. Open-chain exercises usually isolate one particular muscle group, whereas closed-chain exercises recruit a series of muscle groups for teamwork. The leg extension, for example, isolates the quadriceps muscle, but the squat, lunge and leg press recruit the gluteals, hamstrings and quadriceps. Everyday activities require use of multiple muscles, so closed-chain exercises provide a more functional knee-strengthening workout.
Shearing vs. Compressive Forces
Open-chain exercises create shearing forces in the knee, by shifting one of your knee ligaments forward while your shinbone shifts backward. This war between your bones and ligaments creates destabilizing shearing forces on the knee. Closed-chain exercises create stabilizing compression forces, which push the head of your thigh bone together with the head of your shinbone. Aside from stabilizing your knees through compression forces, closed-chain exercises also help you maintain bone density, which might prevent osteoporosis, advises the National Osteoporosis Foundation.
Weight Bearing Balance Exercise
Squats and lunges performed on balance devices take your knee strengthening to the next level. As you perform the movements, your smaller knee-stabilizing muscles, such as your inner and outer thighs, engage and help you maintain balance. To integrate strength and balance, begin with a traditional squat, lunge or leg press performed with resistance to strengthen the muscles. For your next set, reduce the resistance, or eliminate it completely and perform a set of squats and/or lunges on a balance board, a balance disc or a BOSU or half ball.
Hamstring/Quadriceps Balance
Your hamstrings bend your knees, and your quadriceps straighten them. If you stand with your knees in a locked position and your weight shifted backward toward your heels, you might have a hamstring/quadriceps muscle imbalance. Chronic knee hyperextension overstretches your knee ligaments and makes them vulnerable to injury. The exercise ball leg curl provides one of the few closed-chain hamstring exercises. It also engages your gluteal and core muscles, which also stabilize your knees. Lie face-up with your knees bent and your feet on the top of the ball, separated at hip width apart. Peel each vertebra from the floor and create a bridge. Stay in the bridge, and straighten and bend your legs for eight repetitions, then roll back to the starting position. Perform four sets.
References
- Harvard Health Publications: Exercise for Stronger Knees and Hips
- Brian Mac Sports Coach; A Review of Open and Closed Kinetic Chain Exercise following Anterior Cruciate Ligament Reconstruction; Anthony C. Miller
- National Osteoporosis Foundation: Exercise for Healthy Bones
- American Council on Exercise: Stability Ball Hamstring Curl
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