"The routine X-rays indicated that everything was okay and he was going along great, but a C.T. scan showed it hadn't healed on the scar tissue," Hammers physio John Green told the clubs official website.
"Since he has been out of plaster it has not healed perfectly although initial X-rays looked reasonable for the time of healing.
"It is the navicular bone, and it is a difficult situation because this cube of bone in the foot could crumble like a decayed tooth and, in later life, affect his ability to walk.
"In 80% of cases his foot would have healed naturally, which is preferable because a fixation of the bone is not without risk, but some bones are vulnerable and we couldn't take the risk that in 18 months we found that the bone was starting to die.
"Rufus was oblivious to it and it didn't heal normally; he had been running, jumping, hopping, and skipping without symptoms as part of his work and this is a massive setback but Rufus' long term situation is of paramount importance."