Arnold, who lives in a pond near the center, was limping, so the staff took him in for surgery when they discovered he had two fractures on his foot.
They heard a tapping on the clinic door as Arnold was about to leave for surgery.
Arnold's partner had tracked him down and was attempting to gain access to the clinic in order to be by his side.
"She had somehow located him and was agitated that she couldn't get inside," the center wrote on Facebook, adding, "she remained there throughout the entire procedure, watching us work, never moving from the doorway."
The center stated that this was their first animal visitor and that they had to make an exception to accommodate her request for a visit.
Arnold could have been attacked by a snapping turtle or other predators while swimming, according to the center, and surgery was his best chance of survival.
Following the surgery, he was allowed to recover by the doorway through which he could see his mate.
"His mate immediately calmed down and began grooming him through the door," the center wrote, adding that "they both seemed much more at ease in each other's presence."
Arnold's recovery could keep them apart for several weeks.