As previously noted, Samoa Joe has been injured and the injury is not part of a storyline.
WWE.com has provided an update on Joe's injury which occurred during his match on RAW:
“During his match, [Samoa Joe] felt a pop at the bottom of his
foot,” explained WWE Senior Ringside Physician Dr. Chris Amann. “We took a look and believe he has a plantar fascia rupture, which is a thick tissue rupture under the foot. We will get an MRI to confirm. Treatment includes a period of immobilization in a boot with crutches and platelet rich plasma injections.”
For Joe's type of injury, he could recover as quickly as two weeks but recovery could take as long as two months. In a worst-case scenario, Joe would miss the Royal Rumble PPV but not Wrestlemania.
He can't stay healthy for shit, wouldn't be surprised if he's released by the end of the year