B1A4's CNU was belatedly reported to have suffered a serious knee injury. The idol star is also scheduled to be undergoing surgery.

SEE ALSO: B1A4 celebrates 13th anniversary with sold-out fan concert series

According to reports, CNU injured his knee just before the group's album release in August with "Sweet Girl", and the group had to delay their comeback. Fans suspected that something was wrong during promotions as he wore knee pads. Despite the pain, CNU is said to have wanted to continue with the comeback.

A rep from his agency stated that he's damaged the cartilage in his knee, and that he would continue with treatment during promotions as well as a surgery after B1A4's concerts on September 12-13.