It came as a bit of a surprise last December when the Texas Rangers gave the thumbs down to a trade with the Red Sox for Mike Lowell. The deal went south when the Rangers announced that a physical had uncovered a tear of the radial collateral ligament in Lowell's right thumb.

So instead of heading to Texas, Lowell was wheeled into surgery. A mere two months later, Lowell reported to Spring Training and the talk was about whether the former World Series MVP could elbow his way into the lineup. The surgery was almost an afterthought.

"The procedure that Mike Lowell would have had for his radial collateral ligament (RCL) injury of the thumb is relatively straightforward," said Dr. Charles S. Day, chief of orthopaedic hand & upper extremity surgery at Beth Israel Deaconess Medical Center. "With repair and rehabilitation, there was good reason to believe he'd be ready to go in a couple of months."

You might recall that about the same time that Lowell was having his surgery, Patriot wide receiver Wes Welker suffered a knee injury, tearing both his medial collateral and anterior cruciate ligaments. Unlike Lowell's six-eight weeks of recovery, the word on Welker was six-12 months. That's a huge difference.

"There are anatomic similarities and differences between Lowell's thumb injury and Welker's knee injury," Dr. Day said. "Both involve ligament injuries. Ligaments are static stabilizers for joints, connecting bone to bone. The collateral ligaments -- the radial collateral in Lowell's case and the medial collateral in Welker's -- run on the sides of the thumb and the knee, respectively. The thumb and the knee are designed to bend on one axis and the collateral ligaments keep the joint from flopping side-to-side."

Dr. Day suggested thinking about collateral ligaments as attaching two pieces of rope on either side of a hinge joint. That would be similar to how collateral ligaments function. If the rope gets frayed or torn, then the joint can have side-to-side instability while flexing and extending.

"If a partially torn ligament is relatively closely approximated, then it can knit back together with immobilization alone," he explained. "However, if the ligament continues to not stabilize the joint after immobilization, then surgical repair is needed. On occasion, with patients that have a complete tear of their RCL, I will proceed directly with surgery to suture the two ends together. Sometimes I'll place a small wire through the two bones to keep the joint stable while the collateral ligament heals. In six weeks we remove the wire and the rehab can begin."

In Welker's case, doctors immobilized his knee and waited for his MCL to heal completely, and only then undertook a surgical repair of the ACL.

"The anterior cruciate ligament (ACL) connects your femur to your tibia and keeps the bones from sliding too far forward," he said. "It is smack in the middle of the knee, behind the patella and surrounded by synovial fluid or joint fluid. Unlike the collateral ligaments, the ACL has to be surgically repaired. At the risk of over-simplifying the biology, the ACL can't come together on its own because the 'stuff' that signals the body to repair the ligament flows away and gets too diluted in the joint fluid that the ligament bathes in. An ACL repair requires a replacement ligament, often taken from the patellar tendon or the hamstring."

The surgery also involves drilling small tunnels at the ends of the femur and tibia through which the new ligament is threaded and then screwed to the bones. It's a much longer recovery and rehab.

"The healing takes about three months, and the muscles of the leg atrophy during that time. Because the knee is subjected to so much more force and stress than say, a thumb, those muscles have to be built back up to protect the stability of the joint, especially when you consider the sudden stops, starts and changes of direction that a wide receiver is required to do."

The jury will remain out on Welker's recovery for some time. As for Mike Lowell, he's showing no ill effects from his thumb surgery. What he hasn't recovered is an opportunity to play regularly, and he's realistic enough to know that will be tough to do in Boston.