Fears that he had broken a bone have proved unfounded, but the former All-Star will still miss the remainder of the National League due to ligament damage.
McMahon had just returned from a lengthy lay-off with a hamstring problem when he suffered the latest injury in the Healy Park win over Antrim on March 12.
“It’s just ligament damage. It’s good news but he’ll still be out for a few weeks,” said assistant manager Tony Donnelly.
Meanwhile, goalkeeper John Devine is close to his first appearance of the season, after undergoing surgery on a shoulder injury.
Devine could be included in the match-day squad for Sunday’s penultimate Division Two tie against Kildare should Johnny Curran fail to recover from knee and groin problems.
“John Devine is back in training, and is likely to be in the panel as cover if Johnny hasn’t recovered,” said Donnelly.