Denmark's Crown Prince Frederik on Friday had to cancel an appearance at a royal reception for Danish Olympic and Paralympic athletes after fracturing his spine while jumping on a trampoline.

The accident took place at a private event in a gymnasium on Thursday, the royal court said in a statement.

"The fracture is being treated with a cervical collar that the crown prince should wear for around 12 weeks. After that the crown prince is expected to have fully recovered," it said.

Frederik, 48, the eldest son of Queen Margrethe, is known for his keen interest in sports and is a member of the International Olympic Committee.

"When you jump on a trampoline when you are almost 50, then maybe it is not so strange that it goes wrong," Margrethe told Danish athletes in a speech, prompting laughter from the audience.

"He's fine, he just can't take part in this event," she added with a smile.

In 2004, Prince Frederik famously married Australian Mary Donaldson, whom he met during the 2000 Sydney Olympics.

The couple have four children, princes Christian and Vincent, and princesses Isabella and Josephine.