A scientific study last year found that the longstanding knee problems of five Premiership players were caused by microscopic bugs rather than a big boot, and that their source was almost certainly unprotected sex.
On average, each of the players had had knee trouble for eight months before the cause was diagnosed by a blood test. With the average salary for a top-flight player at pounds 10,000 per week, they cost their clubs an average of nearly pounds 500,000 by - so to speak - playing away.
Now John King, a consultant orthopaedic surgeon at the London Independent Hospital, said that the diagnosis of "sexually acquired reactive arthritis" (SARA) "goes through my mind whenever I see a footballer with a swollen knee."
He thinks that the problem is probably surprisingly common - even though it is one that has only just been identified. "A number of people may have had knee operations which were unnecessary," he commented.
The data emerged in a study by Paul Oyudo in a master's dissertation at Queen Mary and Westfield College (WMC) in London. It was followed up by Mr King, [NB NOT DR] who is president of the British Sports Doctors Association.
The QMC study looked at 10 sportsmen with persistent knee injuries which were traced to "sexually acquired reactive arthritis" (SARA). Six of the ten were footballers, and five of those in the Premiership. Five of the ten reported having had over 11 sexual partners by their mid-20s - twice as many as in the general population.
"The level of promiscuity among these sportsmen calls for concern," said Dr Oyudo, who carried out the QMC study, reported today in New Scientist magazine. "Footballers appear to be the greatestculprits."
The mechanism by which the bacteria lead to SARA is unclear, but probably follows an allergic reaction in the knee's tissues, said Mr King. "All you get is a sore, swollen knee. That's why athletes are more likely to notice it."
The study may have a dramatic effect on injury rates in the Premier League next year though. It is unlikely any married footballer will claim to have a knee injury unless there is film of him being kicked.