The pop sound came from my calf. I did have an MRI on the calf which at the time showed a calf tear. I don’t recall whether it was a grade 2 or 3. In addition, I’ve had three EMG tests which have shown a compromised S1 nerve and muscle weakness in both my right calf and right hamstring. My most recent EMG was last month in which the neurologist suggested I have another back surgery so the leg doesn’t become more compromised. Unfortunately, all three EMG test were conducted by different doctors at different facilities. I understand that those tests can be somewhat subjective, so no way to tell if my leg is the same, or getting worse. I feel that my leg has been compromised since the calf tear, with no ability lift my right heel off the ground.
P.S. I have never really had any lower back pain. I still play golf several times a week without a problem, but the walking is quite labored with a limp that gets more progressive as the day goes on.