Boys can grow until age 20 or later. Bones grow out from the ends, known as the growth plates, which are softer than the mature bone. This growth of the long bones in the leg, along with the lengthening of connective tissue, can cause "growing pains." This is a temporary condition, but it is important to limit repetitive movements as well as heavy weightlifting to prevent permanent damage to the joints.
Bone and Cartilage
Bone cells form in the marrow and migrate out in capillary blood to the end plates. The long bones in the leg, called the femur and tibia, are connected to each other with the patellar tendon. The patella, or kneecap, is a bone protecting this junction. Knee and muscle pain in teenage boys can occur during a growth spurt; warming-up and cooling down properly during exercise can minimize the problem.
Good exercise habits include a proper warm-up. The knee joint is especially important to warm up and loosen up to prevent rotational stress on the ligaments from causing pain and injury. A good warm-up is several minutes of jogging followed by light hopping from one foot to another, bending the knee and hip in a "figure 4" stretch, and slowly running backwards. This dynamic stretching for 10 minutes before playing a team sport or working out is a habit that should be maintained for life.
After working out, stretch by leaning against a wall or on a staircase to lengthen the calf muscles. An exercise band or partner stretch for the hamstrings is easy to do by lying on the ground and bringing the knee of one leg toward the chest while leaving the other leg on the ground. Hold for 20 to 30 seconds, then repeat with the other leg.
Teen boys need to be careful about spending too much time one one sport; bones are sometimes weaker than the connecting ligaments during a growth spurt, and stress fractures are common in overworked teen athletes. It is important to have a day of rest in between workouts. Participating in more than one sport, rather than specializing, is also beneficial to cross-train muscles. Adolescent boys can experience significant muscle growth during puberty, but keep the focus on flexibility and endurance during resistance training to stay within safe limits.
If no fracture or inflammation is present, most growing pains should resolve in a few days. Resting the knee and using a cool gel pack on the joint will help. See the doctor for any swelling or lumps, or for pain that last more than a week.