He loves playing football, riding his bike and swimming.
But his doting parents know that Joe is not like other boys – and that he will be in a wheelchair before his 10th birthday.
The bubbly youngster may never get to reach adulthood because he suffers from Duchenne Muscular Dystrophy, a muscle-wasting condition which means he will get weaker year by year.
It's a grim outlook which his family are struggling to come to terms with – but Joe's courageous mum and dad are not letting it beat them.
Stewart and Annette Rush have launched a massive charity fund-raiser to help find a cure for the disease, called Duchenne, which affects only one in 3,000 boys worldwide.
'10 miles for Joe', which more than 100 people are already sponsoring to the tune of £5,000, will see Mr Rush swim 10 miles non-stop at his local pool.
The motto for the day, in aid of the charity Action Duchenne, is Using Our Muscles To Save Theirs.
Mr Rush, 36, who lives in Petersfield but was brought up in Cosham, Portsmouth, said: 'We didn't realise there was a problem with Joe until last year.
'His teacher came to us and asked if Joe was okay because he was falling over all the time and couldn't keep up with the other boys.'
A muscle biopsy revealed that Joe's muscles were not normal.
'At first I couldn't really face it,' said Mr Rush. 'I built a car for a year. When I finished, I realised I would have to deal with it.
'Joe is weaker than other boys. He can't ride a normal bike because he just hasn't got the strength in his legs.'
Joe rides a special light-frame bike and swims every week to keep his muscles as strong as possible.
Mrs Rush, 31, said: 'The biggest thing for us is raising awareness. When we found out we had no idea and had to Google it. We were horrified.
'The only thing stopping finding a cure is money.'
Mr Rush has been training for the event, which will take place at Taro Leisure Centre's 25m pool in Petersfield on May 24. He has been swimming four hours a night – around 420 lengths.
Joe will be sounding the starting horn.
'I am doing all this for Joe,' said Mr Rush. 'Every day we have with him is precious for us.'
To get involved in '10 Miles for Joe' and sponsor Stewart, log on to www.justgiving.com/10milesforjoe All donations will go to Action Duchenne, a national charity working towards finding a cure.