A loading unit configured for engagement with a surgical instrument having a firing rod is disclosed. The loading unit comprises a proximal body portion, a tool assembly, and a knife assembly. The tool assembly is disposed in mechanical cooperation with the proximal body portion. The knife assembly is movably disposed at least partially within the proximal body portion and includes a proximal end positioned to engage the firing rod, and includes a first arm and a second arm. The first arm is biased towards the longitudinal axis via a biasing force. The biasing force is selected to allow the first arm to deflect when the firing rod is advanced. The first arm and the second arm of the knife assembly are configured to engage a firing rod of a surgical instrument as the surgical instrument is being actuated.
