What is causing my knee pain???

[Canadian-Ice]

Hi All,

Looking for some sage advice. Or at least some varied opinions, ideas, and thoughts from the wise.

I have long periods with no pain in my left knee. But just 2 days ago I went on an exercise bike for 10 minutes, and today I get pain just walking and in the pool. It's kind've a pain right in the joint, feels as if my bodyweight is pressing down on the joint space area. Generally no other symptoms. History is as follows.

1. 3 years ago during a wrestling drill I heard a loud pop being taken down by a big guy with my left foot sticking out to one side and the knee going south to the floor. I couldn't extend or bend the knee fully (can't remember which) for about 6 weeks but it healed on it's own.
2. In 2012 left knee MRI shows a bit of chondramalgia in one compartment but otherwise unremarkable. Cartilage loss normal wear and tear for 38 year old active male and same on both sides. Right knee unsymptomatic.
3. Left knee X-ray also shows nothing particularly wrong.
4. Ultrasound shows old injury and queries meniscus tear.
5. 1 Ortho doc thought minscus issue by the MRI, but 3 others plus radiologist said negative.
6. I have mild OA in both hips, mainly my left one.

The symptoms were bugging me walking for a while, but with simple leg curls in the gym, that went away. But still, I can't ride a bike, which is an important part of my recovery plan.

I don't really see why this knee pain would be referred from the hip given it's triggered by exercise bike and doesn't show up for 24-48 hours later after just 10 minutes!

Any thoughts?

Perplexed,