“It’s just growing pains.” It’s one of the most common things parents are told, and sometimes, it’s true. But knee pain in children and teenagers isn’t always as simple as that, especially in kids who play sport regularly.
Knowing the difference between normal developmental discomfort and something that actually needs attention can save your child a lot of unnecessary pain, missed games, and in some cases, long-term joint problems.
Here’s what parents need to know.
What Are Growing Pains, Actually?
True growing pains are a specific (and genuinely common) condition that affects children roughly between the ages of 3 and 12. They tend to appear as deep, aching pain in the muscles of the thighs, calves, or behind the knees, usually in the evenings or at night, and are typically gone by morning.
The key features:
- Both legs are usually affected
- Pain is in the muscles, not the joints themselves
- The child is fine during the day and during activity
- There’s no swelling, redness, or limping
- A gentle massage or warm pack brings relief
If your child’s knee pain fits that pattern, genuine growing pains are a reasonable explanation. That said, it’s still worth mentioning to your GP or physiotherapist if it’s frequent or distressing.
When It’s Probably Not “Just” Growing Pains
The phrase “growing pains” gets applied too broadly and sometimes it masks something that genuinely needs treatment. Here are situations where the cause is likely something else:
The pain is in the joint, not the muscle
If your child is pointing to the knee itself, the front, side, or back of the actual joint rather than the surrounding muscles, that warrants a closer look.
It’s worse during or after activity
Growing pains don’t typically get worse during sport. If your child starts limping mid-game, or the knee swells up after training, that’s a signal to investigate.
There’s visible swelling or warmth
A swollen or warm knee joint in a child is never normal and always needs assessment.
It’s only one knee
Classic growing pains are bilateral. Pain that’s consistently in one leg — especially one knee — is more likely to have a specific cause.
The pain is there every day and isn’t improving
Persistent, daily pain that doesn’t ease over a week or two is worth getting checked out regardless of the suspected cause.
Common Causes of Knee Pain in Active Kids
Osgood-Schlatter Disease
One of the most common causes of knee pain in sporty kids aged 10–15. It causes pain and swelling just below the kneecap, where the patellar tendon attaches to the shinbone. It’s caused by repeated stress on a growth plate during periods of rapid growth — particularly common in kids who run and jump a lot (football, basketball, gymnastics, dance).
It sounds alarming, but it’s very manageable with the right physio guidance and usually resolves on its own once growth slows.
Patellofemoral Pain Syndrome (Runner’s Knee)
Pain around or behind the kneecap that tends to worsen with running, squatting, or sitting for long periods. Often linked to muscle imbalances or poor movement patterns — very treatable with physiotherapy.
Sinding-Larsen-Johansson Syndrome
Similar to Osgood-Schlatter but at the bottom of the kneecap rather than below it. Also growth-plate related and common in active adolescents.
Iliotibial Band (ITB) Syndrome
Pain on the outer side of the knee, often in young runners or cyclists. Linked to hip weakness and training load rather than growth.
Ligament or Cartilage Injuries
Less common in younger children (whose ligaments are often stronger than their growth plates), but increasingly seen in teenagers — particularly ACL injuries in girls playing pivoting sports like netball, soccer, and AFL.
When to See a Physiotherapist
Take your child to a physio if:
- Knee pain has lasted more than 1–2 weeks without improving
- They’re limping or avoiding activity because of it
- There’s swelling, redness, or warmth in the joint
- The pain came on suddenly after a specific incident (fall, collision, awkward landing)
- They’re regularly sitting out of sport or PE
You don’t need a GP referral to see a physiotherapist. An assessment can quickly clarify what’s going on and importantly, give you and your child a clear plan, rather than just telling them to rest and hope for the best.
A Note on “Pushing Through It”
Kids often don’t complain about pain until it’s quite significant, and when they do, it’s tempting to encourage them to keep going, especially mid-season. But persistent knee pain in a growing child is a signal worth listening to.
The good news: most causes of childhood knee pain respond really well to physiotherapy, and with the right management, most kids can stay active throughout their recovery, just with some adjustments.