Why football specifically
Football asks the knee to do a lot of the same things repeatedly: accelerate, decelerate, cut, and strike a ball with a forceful quadriceps contraction. Every one of those loads the extensor chain from hip to shin. In a growing athlete, that chain runs straight through two vulnerable growth plates.
Add three or four sessions a week across school and club, artificial or firm pitches, and a season that runs most of the year, and knee pain becomes one of the most common reasons young footballers see a physiotherapist.
Locate the pain first
Asking your child to point with one finger is remarkably informative. Growth-related conditions are usually pinpoint; joint problems tend to be described with a whole hand around the knee.
- On the bony bump 2–3cm below the kneecap: Osgood-Schlatter disease.
- At the lower tip of the kneecap itself: Sinding-Larsen-Johansson syndrome.
- Vague ache around or behind the kneecap, worse on stairs and after sitting: patellofemoral pain.
- Along the outside of the knee, worse with running volume: iliotibial band-related pain.
- Deep inside the joint with swelling, locking or giving way after a twist: needs assessment.
The three common growth-related causes
Osgood-Schlatter and Sinding-Larsen-Johansson are the same problem at two ends of the same tendon: too much traction on a growth plate. Both respond to the same principles - reduce the highest-impact volume, load the quadriceps progressively, rebuild landing and speed last.
Adolescent patellofemoral pain is different in character. It is less about a single tender point and more about how the kneecap is loaded and controlled. Hip and quadriceps strengthening over roughly 12 weeks is the intervention with the best track record, and it typically takes longer to resolve than the apophysitis conditions.
What to do in the first two weeks
- Halve the highest-impact volume - shooting practice, repeated sprints, jump-heavy drills, rather than stopping football.
- Start daily isometric holds: wall sits or held knee extensions, several sets of 30–45 seconds.
- Use the 24-hour rule to judge each session: soreness should return to baseline by the next morning.
- Check footwear and surfaces; moulded boots on hard ground are a common aggravator.
- Get the weekly schedule written down across school, club and any additional coaching.
Building back
From around week three, the focus shifts from settling symptoms to building capacity: slow, heavy squats, split squats, step-downs, calf raises and hip work, progressed over several weeks. Once the knee tolerates that, landing and deceleration return, then hopping and bounding, then sprinting and cutting, and finally full match load.
Skipping the middle of that sequence is the most common reason a young footballer flares again in their first full week back.
When it is not growth-related
- A specific twisting injury followed by swelling within hours.
- The knee locking, catching or giving way.
- Inability to fully straighten or bend the knee.
- Pain at night or at rest, fever, or feeling generally unwell.
- Pain that has not responded at all to six weeks of sensible load management.