THE SYDNEY Swans have been baffled by the cause of Shane Mumford's recent back issues, but the club discovered on Monday the ruckman has picked up a rare infection from a cortisone injection.
 
Mumford was ruled out of the club's round two clash with Fremantle after waking up on the morning of the game with back soreness, before a cortisone injection appeared to fix the problem and he was cleared to play Port Adelaide the following week.
 
The 25-year-old played well against the Power and thought the problem was solved, until it flared again last Friday, and Mark Seaby replaced him in the side for the second time in a fortnight.
 
Swans coach John Longmire said, after Sunday's victory over North Melbourne, he hoped the problem wouldn't continue to affect one of the club's most prized assets, and the Swans would learn more this week.
 
The re-occurrence of the back issue had surprised the medical staff, but Longmire has revealed to sydneyswans.com.au the source of the problem.
 
"He's actually got an infection," Longmire said.
 
"He had a cortisone injection a couple of weeks ago in his facet joint and that worked and worked well. He was able to play, he played really well, pulled up really well and we thought that was fine.
 
"It wasn't until last Friday that he came into training and was very sore in his back again, and it didn't make sense considering he had played well and then hadn't done much since.
 
"So the doctors got him scanned and found that infection, most likely from the cortisone injection.
 
"It's been sitting there and develops over a period of time and was bubbling away and all of a sudden last Friday he was symptomatic with it.
 
"At least we know what it is and he's on a course of antibiotics. 'Gibbsy' (Swans club doctor Nathan Gibbs) said it's pretty rare.
 
"Hopefully the antibiotics really takes action and he's able to train later in the week. He's no certainty to play this week, it just means we know what it is and we're able to treat it now."
 
It is the second unusual ailment to strike the Swans in recent weeks, with defender Nick Smith missing the past two games with a severe inner ear infection that was causing vertigo.

Smith and Lewis Roberts-Thomson (cheekbone) returned to light training last Friday and Longmire will monitor all three players this week.

Of course the Swans' main injury concern is the compound fracture suffered by young forward Gary Rohan that has ended his season prematurely.

Longmire is a huge admirer of Rohan and said the youngster will do everything he can to get back on the field as soon as possible.

"I've spoken to him, he had surgery last night and he's just recovering today," Longmire said.

"He's OK considering what he's been through. They put a pin in it and it's then just a matter of time.

"His family went back today (to Cobden in western Victoria) and his mum's coming back tomorrow.

"He's a super kid. He missed a lot of footy last year and was fantastic the way he coped with that.

"This is a massive step up again, but he's just a terrific kid and he'll get a lot of support from everyone and he'll work hard like we know he will."

James Dampney covers Sydney AFL news for AFL.com.au. Follow him on Twitter: @AFL_JD