SANDWICH, UNITED KINGDOM, July 13 (Reuters) - U.S. Open champion Jon Rahm put to rest speculation on why his back swing is shortened, explaining that being born with club foot means he has limited mobility in his ankle to play with a full swing. The Spaniard, who clinched his first major last month, has won several titles on the PGA Tour and European Tour with a shortened but efficient back swing which was initially attributed to his "tight hips", much to Rahm"s frustration. Rahm said that being born with the birth defect meant his right leg did not grow at the same rate. "I was born with a club foot on my right leg, which means... my right leg up to the ankle was straight, my foot was 90 degrees turned inside and basically upside down," Rahm said on Tuesday ahead of this week"s British Open. "So when I was born, they basically relocated, pretty much broke every bone in the ankle... within 20 minutes of being born from the knee down... So I have very limited ankle mobility in my right leg. It"s a centimetre and a half shorter. "What I mean by limitations is I didn"t take a full swing because my right ankle doesn"t have the mobility or stability to take it. I learned at a very young age that I"m going to be more efficient at creating power and be consistent from a short swing." Rahm will be looking to join an elite list of players who have won the U.S. Open and the British Open in the same year -- a feat last achieved by Tiger Woods in 2000. The 26-year-old is also looking to become the first Spaniard since three-times winner Seve Ballesteros, who last won the Claret Jug in 1988. "I"m usually pretty good in golf history. I know Tiger has done it. Might have been maybe Ben Hogan has done it too and not many more. It would be pretty incredible to win both Opens in one year," Rahm added. "I did have a sense of relief after winning the first major. I felt like for the better part of five years, all I heard is "major, major, major" just because I was playing good golf -- as if it was easy to win a major championship. "Nobody after Seve has been able to do it, so to give Spain that would be pretty unique as well."