"David has had a difficult time with his knee," chief executive John Williams told the Lancashire Evening Telegraph.
"The swelling is still there after games and it's disappointing for everyone concerned.
"He initially had surgery last February when the problem had been identified with the idea he would then have the summer to recover.
"As a remedy, he is going to the States on Monday to see a specialist. We are not sure yet whether this will entail surgery, but the club doctor, Phil Batty, will be travelling with David and we just have to wait and see."