To those of us without a medical degree it sounds a bit ominous: After not playing a snap as a rookie, 49ers defensive tackle Tank Carradine recently had a follow-up surgery to remove a mass of scar tissue from his surgically repaired right knee.

That complication – the development of scar tissue – is known as arthrofibrosis, which causes stiffness in the joint and can severely limit mobility. At the NFL combine last week, Jim Harbaugh said Carradine’s condition prevented him from fully straightening his right leg, but painted a rosy picture of the 2013 second-round pick’s future. Carradine sustained a torn ACL in November 2012 when he was at Florida State.

“He looks like a different guy now since that procedure,” Harbaugh said. “… I think he’s going to have a great offseason and look forward to his progress very, very much.”

Harbaugh, of course, isn’t a doctor, something he’s often reminded nosy reporters who ask questions about the status of his injured players. With that in mind, I contacted Dr. Bert Mandelbaum, an orthopedic surgeon at the Institute for Sports Sciences in Los Angeles.

Mandelbaum is also president of the Santa Monica Sports Foundation, which is studying ACL tears in the NFL. Among the collaborators on the project is the 49ers team physician, Dr. Tim McAdams, along with team physicians for the Giants, Rams and Browns.

So what could Carradine’s knee complication mean for his NFL future? Mandelbaum said Harbaugh’s optimism isn’t unfounded. Arthrofibrosis, while not common, can generally be resolved with proper treatment and aggressive rehabilitation. Mandelbaum stressed he was speaking in general terms because he didn’t have knowledge of Carradine’s condition.

“I wouldn’t say it’s routine, but when it occurs the team of surgeons will focus on it,” Mandelbaum said. “They’ll take care of it, clean up the scar tissue, take care of whatever manipulations they need and, at the end of all that, the prognosis is very good …

“In general, when you have a significant high-energy injury to the knee – an ACL (tear), an MCL – there’s a direct relationship between the severity of the injury and the amount of scar tissue that occurs. A simple injury? No chance of scar tissue. A more complicated injury. More scar tissue.”

If, indeed, Carradine’s prognosis is good, the 49ers can expect to finally receive a contribution from the No. 40 overall pick in last year’s draft. In 2013, Carradine began the season on the non-football injury list, was inactive for five games and was placed on injured reserve on Dec. 10.

Carradine is one of four players the 49ers have drafted since 2012 who had a serious injury when they were selected. Carradine, running back Marcus Lattimore (4th round, 2013), defensive lineman Quinton Dial (5th round, 2013) and guard Joe Looney (4th round, 2012) have played 90 snaps in five combined NFL seasons.