I did acl reconstruction surgery bk in 2010 until now i can't bend my knee full like before , i feel pain inside my knee , i hear sound when i bend it?

Degeneration: This is likely a progression of a post-traumatic condition. Causes such as arthritis, synovitis (inflammed joint lining), arthrofibrosis (scar tissue build up), a meniscal tear (degenerative), or chondromalacia (softening and fraying of joint surface) with a chondral flap may all be the cause. Check back in with the orthopedic surgeon who did your knee surgery.

Acl: You may have just inflammation or chondromalacia(wear and tear). Recommend an orthopedic evaluation and possible mri.