Jadeveon Clowney underwent microfracture surgery on his injured knee.

Clowney is expected to miss nine months.

The 21-year-old Clowney had knee surgery in September. Per John McClain of the Houston Chronicle, the September surgery was performed on Clowney’s cartilage and his lateral meniscus. According to McClain, Texans G.M. Rick Smith indicated the team knew microfracture surgery — which addresses cartilage damage — was potentially on table at some point.

Clowney was the No. 1 overall pick last May by the Houston Texans.