Potential side effects of knee osteoarthritis injections include joint swelling and pain. They can't be used by people with skin or joint infections. Most injections are made from processed chicken or rooster combs, and shouldn't be used in people with egg or poultry allergies (Euflexxa is safe to use in people with egg allergies).
Occasionally, a severe reaction with swelling, redness, and pain can happen. This is called a pseudoseptic reaction