THE smile on the face of Erraid Davies when she won Commonwealth bronze in 2014 was one of the most memorable moments of Glasgow’s Games.

The swimmer’s achievement in the Para-sport women’s 100-metre breaststroke was a defining image of that very special summer.

That the now 15-year-old Scot, who became the youngest ever Commonwealth medallist, has been deemed ineligible for disability swimming after medical tests will be a blow to both her and her family.

Erraid, from Skeld in Shetland, was told in April she was no longer deemed “disabled enough” to compete in Para sports.

The athlete called for a review of the decision and met experts in Berlin for more tests, but the International Paralympic Committee (IPC) said its original decision would remain unchanged and upheld the decision.

Erraid, who trains with the Delting Dolphins club in Shetland, has Perthes disease which affects one of her hip bones.

No-one really knows what causes Perthes, which is a childhood condition. It starts with loss of blood flow to the head of the femur, the big bone that connects with the pelvis. This results in necrosis of the bone, and the ball-socket mechanism at the joint is affected once the surface of the bone starts to deteriorate. Essentially, a well-oiled process starts to break down.

Back in the day, children would be cemented into A-line casts and consigned to wheelchairs. At one point, surgery was a recognised intervention.

The good news is that, with Perthes, children grow out of the condition (again, no-one seems to know why, but at some point – Eureka! – the blood gets going again.)

The key to managing it in these enlightened times is to minimise lasting damage to the joint while the condition is present.

Apologies if this rough guide to Perthes is a bit basic – this is most certainly a layman’s explanation. But it is also a parent’s.

Our son was diagnosed with Perthes in both hips aged two and a half.

He’d stopped bounding up the stairs and started going up one wee step at a time.There was something up.

His treatment at Glasgow’s Yorkhill Hospital was second to none. But, really, nowadays there is no “treatment”. He was X-rayed every three months to monitor his condition. Meanwhile, we were told he wasn’t to jump. How do you tell a toddler not to jump?!

So he swam. And swam and swam. He joined the local club, competed in mainstream galas and was club champion in his age group. OK, it wasn’t Commonwealth bronze, but it was gold for us.

He was also football mad and he wasn’t prevented from playing. And then there was the Taekwon-Do (neurotic parental googling told us this might help keep him mobile, with a bit of discipline thrown in for good measure). Everyone who needed to know about his condition did, and they understood if he needed to take time out from participating. But we didn’t dwell on it. It was a case of – shhh, whisper it – “don’t mention the Perthes”. We didn’t look on it as a disability, just something that had to be managed as best we could.

And he coped brilliantly. He still jumped, of course. But when his hips were painful he would just quietly sit on the sidelines and watch. And then join in again with added gusto. He never once mentioned how sore it was. But it must have been.

Then the happy day – the Hogmanay before his 16th birthday. The all-clear. No more X-rays. No more being the biggest kid at Yorkhill.

Erraid and her family were said to be “extremely upset and disappointed” with this week’s decision.

After his daughter’s Commonwealth Games win, her father David said: “When she was four she could hardly walk. So the pool was the only thing that kept her fit. She swam her first mile before she was six. She’s been swimming ever since and she’s just got better and better.”

The upset and disappointment for the family is understandable after so much hard work, perseverance and then achievement for Erraid.

But the better and better can get even better. I’ve seen it with my own eyes.