I have had 4 knee surgeries on my left knee but any slight twisting motion makes my pop. it pops at the back of my knee and to the left. help!?

Arthritis/cartilage: Almost anyone that has had 4 surgeries is susceptible to knee arthritis. Popping in the knees can be benign and of no concern, or, if associated with pain, is often a sign of mensical tears, bone spurs and loose bodies. An x-ray or an MRI are often helpful in demonstrating the problem, but you'll need to visit with an orthopaedic specialist to customize a treatment program for you.

See Orthopedist: The popping and pain could be due to a meniscus (cartilage in the knee) tear. See an orthopedic surgeon for examination and possible MRI as a next step.