University of Southern California defensive end Armond Armstead was admitted to USC University Hospital to undergo tests for an unspecified medical condition, Trojans coach Lane Kiffin announced Friday.

Armstead, 20, started 11 games for the Trojans last season and recorded 43 tackles and three sacks. He was expected to start at defensive end as a senior in 2011 after he decided in December to stay for his final season.

"His situation is being evaluated and tests are continuing," Kiffin said in a statement released Friday. "USC's outstanding team of doctors is providing him with excellent medical care."

Armstead, 20, has played both defensive tackle and end during his time at USC but has frequently been sidelined by injuries, including a broken foot and sprained shoulder. He also missed time during fall camp last year with what the coaching staff termed dehydration.

Kiffin said he visited Armstead and his family -- his brother, Arik, is a 2012 commit for the Trojans -- at the hospital on Friday morning.

"He is in great spirits and in stable condition," Kiffin said. "He is looking forward to getting back with his teammates soon."

Pedro Moura covers colleges for ESPNLosAngeles.com.