* Skelton wins first individual gold in seventh Olympics
* Sweden's Fredricson had no penalties but was slower
* Six horses and riders qualified for jumpoff (Adds quotes)
By Caroline Stauffer
RIO DE JANEIRO, Aug 19 (Reuters) - Britain's Nick Skelton won gold in individual show jumping at the Rio Olympics on Friday after a fast and penalty-free jumpoff that none of the five riders who followed could match.
The 58-year-old, who is competing in his seventh Olympics and was once advised to stop riding by a surgeon, went clear on Big Star in 42.82 seconds. It was his first individual medal though he helped Britain to win team gold in 2012.
"Obviously I was first to go and I thought in my mind to go as fast as I could but be safe... I tried to put a bit of pressure on everyone else. Luck was on my side," said Skelton.
Sweden's Peder Fredricson took second as the only other rider in the jumpoff to score no penalties but he was nearly a second slower than Skelton's pace.
Canada's Eric Lamaze took bronze. The 2008 gold medalist and final rider to go, Lamaze jumped a quick round on the mare Fine Lady but knocked over a rail.
"I knew what I had to do... Nick was very quick and forced all the riders to go at top speed. I knew there was still a spot for a medal with four faults," he said.
Skelton, who is the oldest British gold medallist since 1908, spent much of the past two years nursing Big Star back from an injury and admitted to battling back pain himself.
After a fall in 2000 snapped vertebra in his neck in two places, Skelton's surgeon advised him to give up riding or risk a fatal injury.
"I'm lucky just to get this horse here," Skelton said. "This has capped my career. I've been in the sport a long, long time. To win this now at my age... it's amazing."
Skelton is the second British equestrian to win gold in Rio, after Charlotte Dujardin won the individual dressage competition on Monday.
Six of the world's top show jumpers competed in the jumpoff to determine medals after no clear winner emerged from the two scheduled rounds on Friday.
London 2012 defending champion Steve Guerdat of Switzerland had one rail down. Sheikh Ali Bin Khalid Al Thani, part of Qatar's first-ever Olympic show jumping team, and Kent Farrington of the United States each had two rails down.
The jumping qualifying rounds that started on Sunday gradually narrowed down a field of 70 Olympic show jumping horses and riders to the final six. (Editing by Neil Robinson and Clare Fallon)