Pop when lifting knee

Hi everyone

Got a question, when sitting on the sofa today I lifted my leg bent and straightened it out using quads to get off the sofa. Just before it straightened there was a hollow pop and a sharp bit of pain that went away quickly.

No swelling, but wondering if this is bad, or just scary tissue?

I'm 6 weeks post ACL recon, medial and lateral meniscus repair and LET. Have decent rom (125) and doing seated knee extensions, so not an unusual movement really.