Hello,
Any degree of limping that lasts for more than a few days should be seen by a veterinarian. The only exceptions to this is a dislocated hip which should be seen immediately to try to put it “back in the socket”. Infection is the other thing I worry about. There is usually wound and most often pets are quiet and not eating well.
The most common knee injury we see that causes limping is a cruciate rupture. You will need a vets help to diagnose this.
Hello,
If the limping doesn’t resolve with rest and there is swelling then I think that you need an Xray.