Re: knee injury
As someone who has had 7 knee surgeries, two of which were major joint reconstructions, I can tell you with reasonable confidence that you have torn meniscus, a/k/a torn cartilege (this is my lay opinion, not legal advice or a medical opinion). Given the deteriorating condition of my knoee, I constantly develop the painful condition you describe, which feels like a painful snap or pop, causing greeat pain, especially when bearing weight.
A routine arthroscopic procedure (knee scope) can probably fix it and reduce or eliminate the symptoms altogether.
The longer you leave it untreated, the worse it will get, as the knee releases fluid in response to the tear, and over time the fluid eats away at and kills off additional cartilege, which leads to more fluid, etc, and the condition snowballs upon itself.
Knee scopes are 45 minute procedures, done as an outpatient day surgery. You can be back on your feet within a few days, back to work within a week or so. See an orthopedist.
Because knee cartilege also deteriorates with wear and tear and naturally as we age, I don't think you have a claim against your employer for causing the condition. That depends, however, on your specific circumstances. Go see the ortho and let him tell you what he thinks.
This is NOT legal advice or a medical opinion. Just words from a fellow knee pain sufferer.