I'm no doctor but, this doesn't sound good.
"Johnson has an osteochondral defect in his femur, meaning he has no cartilage in a spot on the knee. He has had injections of a gel designed to lubricate the joint in the absence of cartilage, but Johnson knows he will battle this the rest of his career.
“It'll be something I have to monitor all the time,” he said. “I'm fully prepared to pitch with a little bit of swelling in my knee, I'm fully prepared to pitch with pain in my knee occasionally. I'm prepared to do those things as long as I'm being an asset to the team when I got out there.”
http://www.aztrib.com/index.php?sty=7264
"Johnson has an osteochondral defect in his femur, meaning he has no cartilage in a spot on the knee. He has had injections of a gel designed to lubricate the joint in the absence of cartilage, but Johnson knows he will battle this the rest of his career.
“It'll be something I have to monitor all the time,” he said. “I'm fully prepared to pitch with a little bit of swelling in my knee, I'm fully prepared to pitch with pain in my knee occasionally. I'm prepared to do those things as long as I'm being an asset to the team when I got out there.”
http://www.aztrib.com/index.php?sty=7264