Newkirk, who was averaging 20.3 points through 12 games, is scheduled to undergo surgery in the next few weeks.
He went down with the noncontact injury during a 69-63 victory over George Washington on Friday that pushed the Hawks' record to 7-5.
"This is certainly disappointing to all of us in the Saint Joseph's basketball program. Our thoughts and concern go out to Shavar and his family," coach Phil Martelli said. "We're fully supportive of him, academically and socially and as he makes his return to the basketball court, bigger, stronger and better than ever. His teammates have expressed the same level of support."
Saint Joseph's next plays at Rhode Island on Tuesday.