Growing Knees

For Young Learners

Structure and Location

Your bones are not solid all the way along while you are growing. Near each end there is a disc of softer cartilage called a growth plate. New bone is added there, and that is how your bones get longer.

The knee has two of the busiest growth plates in your whole body, one at the bottom of the thigh bone and one at the top of the shin bone. Between them they produce roughly two thirds of the length of your leg.

There is another growing spot at the front of your shin, just below the knee, where the big tendon from your thigh attaches. If you press there and it feels tender, that is why.

Function

Growth plates close when you finish growing and turn into ordinary solid bone. That happens at different ages for different people, usually somewhere in the mid to late teens, and generally a bit earlier for girls than for boys.

Until then, the growth plate is the softest link in the chain. It is weaker than the ligaments and the tendons around it.

Clinical Relevance

That one fact changes everything about young knees.

Take an adult and a fourteen year old, give them exactly the same awkward landing, and they can end up with completely different injuries. The adult is more likely to tear a ligament. The fourteen year old is more likely to injure the growth plate instead, because that is what gives way first.

It is also why growth plate problems do not show up well on an ordinary x-ray. The growth plate is cartilage, and cartilage does not appear on an x-ray at all. So a doctor who presses on the bone near your knee and finds it tender takes that seriously even if the x-ray looks normal.

Growth spurts are worth knowing about too. Bones lengthen before muscles and tendons catch up, so for a while things are tighter than they were, and knees often ache during that stretch. It passes.

None of this means you should stop playing sport. It means a knee injury in someone still growing is checked properly rather than shrugged off.