I worry that my sports-mad 11-year-old son is setting himself up for orthopaedic problems later in life because he plays football at least five times a week. I would rather he went swimming. Am I fretting unnecessarily?
Name and address withheld

You are probably over-reacting but justifiably. One often hears horrific stories of children who have trained too much.

The reality is that, unless the children undergo extreme training, they are perfectly able to cope. The Training of Young Athletes study, conducted between 1987 and 1992, found that the musculo-skeletal system of young athletes is able to withstand most of the stresses and strains of intensive training at a young age. Nevertheless, football was, with gymnastics, the most injurious of the sports studied, given its contact nature. If a child injures a joint, for example by dislocating it, or damages a ligament (in soccer, the most commonly injured is the anterior cruciate ligament of the knee), then you are right: in the long term, arthritis of that joint may ensue. Again, these are relatively rare lesions in this age group, and they may occur in daily life as well.

Unless your son is likely to become the next Ronaldo there is a lot of sense in letting him play a different sport every day of the week. It will do wonders for his motor skills and encourage balanced body growth and development.

· Professor Maffulli is a consultant orthopaedic and sports injury surgeon at Keele University medical school. If you have a question for him, email fitness@theguardian.com