Hello. My name is Jonathan. I'm 19 yrs old. I had ACL reconstruction (hamstring graft) done on October 2nd 2012. Everything been going very well. I've been going to the gym 4-5 days a week, lifting weights and also using the treadmill, and the bicycle to rehabilitate my knee. I have had no problems at all. Until 2 days ago I noticed that my knee (operated knee) has been cracking every step I take, when the knee extends. But it will only do so for "X" amount of minutes, And then it wil stop cracking. But it will come and go, it is very annoying and frustrating due to the fact that I have not have any problems up until this point. I have been doing squats and dead lifts at least once a week with about 135 lbs. with NO PAIN in the knee what so ever. Keep in mind I use a sports brace to prevent injury. I also noticed today that I have a pea sized lump under the skin, right above the surgical scar. I am very worried. Please help me!