yay! a topic i can totally speak from experience on!
O.k., I hate to play favorites but my little mali, quinn, really has the most personality out of any of my herps. quinn was purchased as a captive bred hatchling when she was still teeeeeny tiny. she also was born with 1 club foot. i think that it is probably caused during development, since she was born with it. perhaps it has to do with conditions that the eggs were maintained with? regardless, the club foot has not slowed her down or hindered her in any way. she's my little (now gravid!!) angel.
as long as your uro is healthy, i wouldn't worry about it. perhaps in the wild it would be a problem (she doesn't move quite as fast as my other uros, but that could also have something to do with the fact that she is bloated and mostly blind in one eye). personally, i think it adds character.
hope you enjoy your little club-footed addition 
here's a good view of little quinnie's club foot, and her big ol' swollen belly!

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1.2 Mali Uromastyx (Ricky, Quinn, Anna)
0.1 Yellow Ackies (Roxie)
1.0 Timor (Zealot)
Emily
www.egomantra.com/npoh