Contact dermatitis or skin inflammation
Bites or stings directly to the inner knee can cause swelling, pain, and irritation around the site. Infrequently stings or nibbles can form into a contamination if microscopic organisms get in. Signs include delicacy, warmth, and release or discharge from the bite site. Erythema likewise happens around the site of contamination. On lighter skin, this shows up as red. On more obscure skin, the surrounding region may look purple or burgundy.