Radiesse has a very high cohesivity and does not migrate. Even when injected, it does not like to be massaged into a different shape or location than when injected. This is a desirable quality for certain areas of the face, but makes it undesirable for other areas such as under the eyes.
Radiesse could not have seeped under the muscle. It would have had to have been injected there originally. Radiesse is a much denser filler than hyaluronic acid fillers like Restylane and Juvederm, so more than likely the hardness you feel is the actual filler material itself.
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