Cross-training is the process of incorporating secondary types of exercise into an existing workout plan to promote greater gains in strength and endurance. To ensure optimal results while cross-training with a knee injury, be sure to keep the intensity of exercise in a moderate zone. Wearing a supportive knee brace, choosing the right types of exercise, and listening to your body are also crucial for those who want to cross-train with a knee injury.
Identify when and why the knee injury took place. If you have a stress fracture -- often a sign of aerobic overtraining -- you'll need to change the type of cardiovascular exercise in which you participate. If you have a strain or sprain to one of the ligaments, tendons or muscles surrounding the knee, you may have musculoskeletal instability, which can be resolved by making changes to a resistance training program.
Add new types of aerobic exercise to your existing workout routine, says the American College of Sports Medicine. If you injured your knee while walking or jogging, switch to swimming. If the injury occurred while riding a bicycle, use an elliptical machine. Whatever the cause of your injury, you should cross-train aerobically to avoid placing the same type of repetitive stress on your knee.
Engage in various types of resistance training. Include weight lifting exercises that target the muscles of the lower body -- including the hamstrings, quadriceps and calves -- to build muscle size and protect the knee joint. If you injured your knee during resistance training, choose exercises that work the same muscle groups but target them in a different way. Replace lunges with squats, for example, or substitute calf raises for step-ups.
Maintain a safe intensity with each exercise. Work at a moderate intensity level to build strength and endurance while preventing excessive strain on the knee. The Centers for Disease Control and Prevention encourages exercisers to use to a "talk test" to maintain proper intensity: If you can hold a conversation but not sing a song you are working out at a safe intensity.
Wear supportive equipment, such as a brace, to safeguard the injured knee. The appropriate style of knee brace may vary substantially, and some are designed to be worn at all times while others are intended for use only during physical activity. The brace should snugly around the knee. A brace that is too tight or too loose may actually have a detrimental effect.
Listen to your body. Stop exercising if you experience moderate to severe pain, which may indicate that your body has not sufficiently recovered to allow physical activity.