A meat ball on a dog's front leg joint may be caused by mosquito bites, arthritis, joint effusion, or tumors. It is best to take the dog to the pet hospital for examination to confirm the cause and then carry out targeted treatment. , to avoid delaying the condition. If it is a tumor or joint disease, a treatment plan needs to be formulated according to the condition; if it is a mosquito bite, just apply anti-inflammatory ointment to the dog.