my 92 year old motherhas large reddish blue areas coming up on her ankles and lower legs, which would not be too much of a concern, because of circulation and also because she bruises very easily. One of those bruised areas is accompanied by a large knot, about the size of a half dollar. I would think she had hit her leg, but she says it doesn t hurt, and doesn t remember hitting it. Could this be a blood clot? She has arthritis and Parkinson s disease.