American Sandi Morris won the event with a best attempt of 4.62m. Katerina Stefanidi of Greece finished second, the only other competitior to clear 4.52m.
McCartney's coach Jeremy McColl said the conditions were blustery and problematic for all the vaulters.
To try and safeguard against the wind factor, McCartney had dropped back to a 10-step runup, rather than the 14 paces she'd been working successfully with this season.
"She got hit by a little bit of wind on the takeoff and got tangled up with her feet on the bar," he said from Birmingham.
McCartney had never had this type of mishap before. He said there was a reason why she initially looked okay and walked across to the side of the track before icing the left foot.
"It's been diagnosed as fat pad bruising, from the impact. It doesn't come up straight away.
"Eliza took a few steps and straight after that it got really sore. We had to ice it to try and get the inflammation down before heading to hospital."
The scans have been encouraging, with nothing showing up, other than a lot of inflammation around the impact point.
"We've been told three days with nothing weight bearing and plenty of icing. We'll know more after three days as to how bad it is for the rest of the season."
McColl said McCartney was upset "in general" with how the day panned out.
After having her best season so far, with three personal best vaults, McCartney has her eye on cracking the 5m barrier, only achieved by two women outdoors, today's winner
Morris and the great Russian Yelena Isinbayeva.
There are three events left on McCartney's calender, a meet at Beckum, Germany on August 26, the Diamond League final in Zurich four days later and a Continental Cup teams event in Ostrava in the Czech Republic, where she is due to represent Asia-Oceania.
Beckum is problematic but McColl's fingers are crossed that McCartney will have recovered in time for the last two.
