SANTA CLARA The "bee sting" that Ray McDonald felt in his right arm three days ago turned out to be a partially torn biceps tendon, the 49ers defensive end said Tuesday.
McDonald said the injury shouldn't keep him out of any games, and he plans to start in his usual spot Sunday against the Cardinals. He said he'll have surgery to repair it after the season.
"It's going to be sore," McDonald said. "But it should be fine."
McDonald has missed only one start since the 2011 season. He suffered the biceps injury in the third quarter Sunday against the Texans when he was shedding an offensive lineman en route to sacking Matt Schaub. He immediately began clutching his arm and did not play another snap.
McDonald suffered what is known as a proximal tear, which means it was at the shoulder end of the biceps muscle. That's preferred over a distal tear at the elbow end, in which the biceps often retracts toward the shoulder and typically requires immediate surgery.
"We may have dodged a bullet there," coach Jim Harbaugh said on KNBR radio Tuesday. "It looks like Ray might have walked one off."
It was the second consecutive week Harbaugh used "dodged a bullet" to describe an injury to a starter. Against the Rams in Week 4, left tackle Joe Staley went down with what appeared, from Staley's reaction, to be a serious leg injury. Instead, there was only a minor ankle sprain and Staley started, and played well, the following week against the Texans.
McDonald said he hasn't lost any strength in the arm at this point, but Dr. Dan Solomon, an orthopedic surgeon with Marin Orthopedics and Sports Medicine in Novato, said that's a possibility as the season continues. Solomon also said it's easier to repair the injury immediately than it is several months later. He said the muscle tends to atrophy a bit and the tendon can roll up on itself.
"It doesn't get any easier," he said of delaying surgery. "But I've fished them out three months down the line."
Loss of strength was a concern when the team's other starting defensive end, Justin Smith, partially tore his triceps tendon late last year. Smith ended up playing with the injury as the 49ers made their playoff push but was not nearly as effective as he was prior to the injury.
The triceps, however, is larger than the biceps and has a greater impact on overall arm strength. McDonald said his biceps looked "a little funny" but was told it should function normally.
"It's too early to tell," he said of how the injury will affect him. "I'll know more as the week goes on."
Solomon noted that quarterbacks John Elway and Brett Favre suffered similar biceps injuries and that Elway's Super Bowl victories came after the injury.
The 49ers have Tony Jerod-Eddie and Demarcus Dobbs in reserve at defensive end. And rookies Tank Carradine and Quinton Dial could be available later this month. Carradine, who is nearly 11 months removed from an ACL tear, said he is back to full speed and strength.
"I started feeling normal at nine months," Carradine said. "I felt like I could go. But I still had to wait until I got the say-so from (head trainer Jeff Ferguson) and them. But I feel great."
Read Matthew Barrows' blogs and archives at www.sacbee.com/sf49ers and listen for his reports Tuesdays on ESPN Radio 1320