i also have a medium size lump just below my knee now, near my surgery scar, i don't know why, it doesn't hurt unless i really push kind of hard on it. the lump is the size of a half dollar.

Might be cartilage. Not sure if an MRI will detect it...but if I remember correctly, you'll be able to identify the cracking on an MRI.

i had acl surgery 6 months ago. my knee recently started to pop and crack when i bend it. i talked to my therapist about it and he doesn't know what it is either.

I had ACL reconstruction 1 week ago. I started physicall therapy 3 days later. Light workout, mostly stretching and talking about therapy. Later that night in bed I felt a pain like a pop. I got up iced my knee and rested. The next day my knee was very swollen and sore. My wife and I went through the take home exercises. Shortly after I felt like a knot on the back of my knee and became very difficult to bend. I also have considerable swelling in my shin, it is very painful and sore to the touch. Has anyone else had simillar issues?

My shoulder does this they call it crepitus apparently its nothing to worry about! this normally develops in joint injuries!!

Crepitus is a clinical symptom in medicine that is characterized by a peculiar crackling, crinkly, or grating feeling or sound under the skin, around the lungs, or in the joints. Crepitus in soft tissues is often due to gas, most often air, that has penetrated and infiltrated an area where it should not normally be (for example, in the soft tissues beneath the skin).

Crepitus in a joint can indicate cartilage wear in the joint space. The term "crepitus" is taken directly from the Latin "crepitus" meaning "a crackling sound or rattle." Typically crepitus is a grinding noise coupled with a sensation in the affected joint. Crepitus can occur with or without pain.