Penske Racing's Brad Keselowski was able to put in a full day at Pocono Raceway, running in both practice sessions ahead of Sunday's Good Sam RV Insurance 500 Cup race.

Keselowski's participation had earlier been in doubt after he suffered a 100mph accident at turn 1 on the Road Atlanta road course during testing. Although Keselowski was able to exit he car under his own steam, he was airlifted to a local medical centre for "precautionary" evaluation which took several hours.

"The left front tyre ended up where the brake pedal was supposed to be," Keselowski said. "But the seat itself was intact and what I feel like got me hurt was that the feet area was compromised. Being a guy with long legs, [the damage] just shoved my legs back into my torso, into my hip and it was very, very painful."

At the time, Keselowski reassured his fans via Twitter that he was okay and that the X-rays had been clear, although he also posted pictures of his badly swollen left ankle. It's now emerged that Keselowski has in fact suffered a small fracture. The injury - technically known as an avulsion fracture - is caused when a tendon or ligament pulls off a piece of attached bone, where the fracture occurs. But after meeting with NASCAR neurosurgeon Dr. Jerry Petty and a specialist orthopedist in Charlotte on Thursday, it was confirmed that Keselowski should be able to race at the weekend with no restrictions.

"Mr. Keselowski saw an orthopedic surgeon this afternoon who indicated that he would be able to put weight on the foot as necessary and should not be inhibited in any way," said a statement from Penske Racing, which confirmed that "he would be able to compete this weekend at Pocono Raceway." However, he's still very bruised and has pain when walking, so the decision to pull Keselowski from double-duty in the weekend's Nationwide Series race at Iowa stands.

Initially it had been thought that Keselowski would at least also have to sit out Friday Cup practice at Pocono, and so Sam Hornish Jr. was on standby to take the #2 car out if that proved to be the case. However, Keselowski took to the track on Friday as normal and experienced no problems, running tenth fastest in the midday session, and eighth in the afternoon session despite a spin that left him limping away from the car in turn 1. Ryan Newman and Kasey Kahne topped the two session timesheets respectively.

(Full Cup practice times and positions available.)

"I consider myself a lucky guy to walk away and be here," he said on Friday. Asked if the accident was preying on his mind at all, Keslowski admitted: "I have checked my brakes a couple extra times before each corner."

That released Hornish to head to Iowa Speedway a day earlier than expected, and Hornish was therefore able to drive Keselowski's #22 in Friday practice as well as the originally-planned Saturday qualifying and evening race. Hornish was fourth fastest in the #22 Dodge in the afternoon practice session topped by Roush Fenway's Ricky Stenhouse Jr. and Turner Motorsports' Jason Leffler.

Initially, Penske had planned to keep Hornish close to hand in Pennsylvania and allow development driver Parker Kligerman to handle the Friday Nationwide duties. Instead, Kligerman was able to return to running in the Camping World Truck Series Friday practice session at Pocono where he drives the #29 for Brad Keselowski Racing. He was 15th fastest in the Friday sole practice session ahead of Saturday morning qualification and the afternoon's Good Sam RV Emergency Road Service 125 race; Kevin Harvick, Todd Bodine and Kyle Busch were the three fastest trucks.