I have an appointment with the orthopedic surgeon tomorrow to go over the results of the MRI. It will be good if the pain in my left knee is caused by tendinitis or some other transitory issue, bad if I have some abnormality such as a meniscal tear. Problem is that someone my age has around a 40% chance of showing some abnormality in a knee, runner or not. And no guarantees that the suggested remedy - such as surgery - will necessarily relieve the pain and solve the problem.
More likely than not, I will opt for a cortisone shot in the short term, see how that goes and then re-evaluate the situation in 6 months or so. Right now, my knee is hardly wrecked. In fact I ran 6 miles (easy) this morning with minimal discomfort. I'm convinced that with a regular daily program of stretching (especially the overly tight hamstrings!) and some quad strengthening, I can avoid any potentially risky surgery.
Like everybody else in this predicament, of course I have been surfing the net in search of pictures of MRI's of normal and abnormal knees, normal and torn menisci, accounts of meniscus surgery and so on. There's both good and bad out there, and I came across some rather disconcerting reports of failed surgery. One unfortunate Canadian had a small lipoma removed, which became a more complicated procedure when it proved to be a cyst. In the end the guy ended up with a very nasty permanent scar on his leg. It reminded me of our first Boxer - Homer - who had a benign growth on his head. I dropped Homer off at our local vet and picked him up again later the same day, seemingly ok except for two big band-aids on the very top of his head. Unfortunately, when it came time to take the band-aids off, it became clear that our beautiful dog now had two massive Frankenstein’s monster scars on the top of his head. From show dog to mutt in a couple of days!
Update: It appears I do have a horizontal tear of the posterior horn of the medial (inside) meniscus. Oddly enough though, this is not what is causing the pain in my knee. The pain is on the lateral (outside) of the left knee, and is likely caused by friction where the iliotibial band attaches to the tibia. The doctor gave me a cortisone shot for that - and I will have to lay off running for a few days to let things settle down. Will continue with quad strengthening program and upper body & core workouts. Until the medial meniscus tear becomes symptomatic, I am not considering surgery to repair it. Let sleeping dogs lie.