Leg numbness for a long time

My son (9) has been experiencing numbness in his right leg for the past 2.5-3 years. It covers the lower area of the leg from the ankle up for around 5 inches. Although it is very common during the evenings the numbness is present during the day as well. My son says that it disappears only temporarily while he is running or otherwise being physically active.

I have consulted the paediatrician of my son several times. I have also consulted an orthopaedist. Both of them, though without performing any examination or test, have told me that this numbness comes as a result of my son growing. Nevertheless, I am being quite concerned as the numbness is persisting for such a long time and - according to my son - it is getting worse.

I would really appreciate your opinion. Would you recommend performing any tests (such as CT or other screenings)? Thank you very much.