A knee injury forces the defending champion to pull out of the race.
One researcher thinks so.
It may actually be good for your joints.
Olympic champion says he has knee problems.
Gebrselassie set to return to competition in Vienna.
The Ethiopian champion has been battling injury for over a year.
Knee problems continue to plague him.
After missing his 2010 goal race due to a knee injury, T.J. Murphy is committing himself to good health in the new year.
With one week to go until the Zappos.com Rock 'n' Roll Las Vegas 1/2 Marathon, T.J. is dancing around a nagging knee issue.