Lions coach Ian McGeechan names his squad on April 21 and will be sweating on Henson's fitness after the golden boy of Welsh rugby left the Ricoh Arena in Coventry on crutches.
An Ospreys statement read: "Gavin Henson met with a specialist and had an MRI scan today and we are now awaiting a formal report and feedback on his condition and prognosis.
"We will be fully informed as to the extent of his injury in the next 24 hours, and will issue a further update accordingly."
Henson, 27, made one Test start for the Lions on the tour to New Zealand which ended in whitewash four years ago. It is the latest setback for Henson, who spent much of last year sidelined with injury.
The Ospreys star has made just 11 starts for Wales since 2005 following ankle and Achilles trouble, although started in all of Wales' Grand Slam games of 2005 and 2008.