05/19/2014 04:49 pm ET Updated Jul 19, 2014

Growing Pains vs. Cancer: Why You Should Take Your Kid's Knee Pain Seriously

Christian MartA-nez Kempin via Getty Images

"My knee hurts," complains the young boy or girl. "You're okay. It's just growing pains," replies the mother or father. This is a common conversation with young people and their parents every day. And, overwhelmingly, the young person's pain is simply from overuse in sports, playing and even perhaps growing rapidly.

Many children develop a self-limiting, albeit painful, syndrome named for two physicians: Osgood-Schlatter's disease or syndrome. The typical age range for this problem is 9-16 years of age, and it tends to occur during what is known as peak-height velocity (growth spurt). The rapid growth of the long bones coupled with forceful contractions of the quadriceps muscle (large muscle in the front of the thigh) pulls its attachment on the bump on the front of the child's lower leg bone (tibia) below the knee cap (patella). Because the bone is immature and not very strong, the repeated pulling on this attachment (tibial tuberosity) causes repeated subacute injuries to the tuberosity, and the attachment starts to pull away from the rest of the tibia.

Too much jumping and training can trigger this syndrome, which is quite painful and will usually stop the young athlete from continued training. But before the pain reaches this level of severity, the child will complain, "My knee hurts." In this case, the pain stems from rapid growth and too much training, and it will resolve when the growth spurt slows and the training load is diminished. A similar problem occurring at the bottom of the kneecap (patella) is also named for the physicians who identified it: Sinding-Larsen and Johansson syndrome. The child will complain of knee pain with this treatable syndrome as well.

The reason complaints of knee pain in a child should not be taken lightly -- especially if the child reports that the pain hurts at night, hurts more at night, or wakes the child at night -- is that these could be signs of a very serious form of bone cancer called osteosarcoma, which occurs in young people. Sixty percent of the occurrences are in the knee, with approximately 42 percent in the femur (thigh bone) and 19 percent in the tibia (lower leg bone). Other less common locations include the humerus (upper arm bone), pelvis, jaw and skull.

The age range for osteosarcoma can go up to 30 years of age. And while adults experiencing its symptoms are capable of seeking care on their own when their pain doesn't stop, children can only tell their parents, teachers, coaches and perhaps school nurses. Osteosarcoma is a very malignant process. It spreads fast and can have severe consequences. While the management of osteosarcoma is improving, this cancer -- if not caught in time -- often requires radical intervention to save the child's life.

So, if you have found yourself telling your child that his/her knee pain is "just growing pains" too many times, it may be worth a visit to a health care provider for a diagnostic work-up.