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Jets running back Chris Johnson had knee surgery earlier this year, but he nevertheless passed a physical on his way out the door in Tennessee and on his way in the door in New York.

Despite being healthy enough to play professional football, that could change in time.

According to Adam Schefter of ESPN, the Jets have “some concerns” about Johnson’s knee. Schefter specifically reports that the knee has arthritis. Which means that cartilage is either gone or disappearing. Which means that Johnson could have chronic issues with the knee as his career continues.

Johnson disputed the report during his introductory conference call with the Jets. Johnson said there’s no arthritis in his knee.

Either way, it hasn’t stopped the Jets from reportedly paying Johnson $3 million to sign. Or from paying him another $1 million in salary this year. But it could put a cap on the number of years that Johnson will be able to play, for the Jets or anyone.