To take a couple of shots in the dark, we have to figure with surgery required it is not one of the more common types of foot injuries or problems like plantar fasciitis or turf toe. Rather at 6 foot eight and 360 pounds it's likely some type of stress fracture injury to one of his tarsal or metatarsal bones, and it's just not healing in part due to his size.
There are a couple of conditions like this, one called navicular bone stress fracture and the other one a Lis franc injury at a tarsal metatarsal joint These usually occur from trauma but at his size it could be a repetitive stress type of injury, then the deformity can occur as a result and this can irritate not only the bones and ligaments but create some neurologic compression of the nerves in the foot all of which can cause pain symptoms.
That would be my best guess, more rarely you can see another fracture and/or stress related injury that results in a lack of blood supply to one of the bones down there, and that can result in what is called an avascular necrosis which pretty much always requires surgery.
