Eagles duo Oscar Allen, Elijah Hewett to have surgery

West Coast's Oscar Allen has suffered bone bruising and cartilage damage. (Richard Wainwright/AAP PHOTOS)

West Coast have revealed that Oscar Allen's knee injury is worse than first thought, while emerging midfielder Elijah Hewett is also set for a lengthy stint on the AFL sidelines.

Scans earlier this week showed Allen had bone bruising on his knee, but it has since been discovered there is also some cartilage damage.