A complex joint consisting of ligaments, muscles, cartilage and tendons, the knees can be a vulnerable spot during athletic or fitness activity. It is for this reason that fitness trainers and teachers often warn against locking out your knees, or hyperextending your leg, when working out. When the joint is locked, the stress is taken off of the supporting muscles and placed onto the knee; as a result, the soft tissue in the knee becomes damaged, greatly increasing the risk of a knee injury. Being aware of your body, balancing your muscles and working out with proper techniques can help keep your knees in the correct position and decrease your chance of sustaining an injury.
Choose a resistance level that matches your fitness ability for all standing and leg exercises, such as squats, leg extensions, leg presses and standing barbell curls. Using weights that are too heavy for your leg muscles to handle can cause you to lock your knees for extra support. Pick a resistance level that allows you to complete at least eight and no more than 12 repetitions with proper form.
Shorten your stride when running or walking; an exaggerated stride can cause you to lock your knees as you extend your leg. An indication that your stride is too long is if your leg lands in front of you, rather than under your body. Keep the knee joint soft throughout the entire stride cycle and allow it to naturally bend when your foot hits the ground.
Strengthen your core to improve the alignment of your legs and feet, which can help you to properly activate the muscles of the lower extremity and reduce the stress on your knees. A weak core, especially weak glutes, can destabilize your pelvis and pull it off-center. The effect of this can travel all the way down your legs. Train your core, which includes your abdominal muscles, glutes, lower back and hips, two to three times per week. Examples of efficient exercises for the core include planks, bird-dogs, back extensions, deadlifts, bridges and abdominal crunches.
Perform resistance-training exercises that target your quadriceps, hamstrings and calves two to three times per week. Weak leg muscles can make the knee do double duty to provide stability, strength and power. Include exercises such as squats, lunges, leg presses, deadlifts and leg curls in your fitness routine. Execute three exercises per workout; aim for three sets of eight to 12 repetitions for each exercise. Vary your resistance methods to avoid hitting a plateau by including barbells, dumbbells, kettlebells, resistance bands and cables.
Stretch regularly to keep your muscles flexible, elongated and supple. Tight quadriceps, for example, can be difficult to activate properly and may lead you to lock your knees for extra support. Stretch for 10 to 20 minutes at the end of each workout. Hold each stretch for 20 to 30 seconds. Breathe deeply while stretching, inhaling through your nose and exhaling through your mouth.