The former Rennes winger joined Toon on Friday and he says he has been fully fit for months.
"Frankly, those rumours aren't anything," he told L'Equipe. "I am perfectly fit, and capable of playing again.
"I resumed individual training sessions at Rennes late last season and I could have played the last match if the club wanted.
"I am a little disgusted to read rumours like that because I know it could affect the rest of my career."