As originally posted on The Cub Reporter
5/24/11 by Dr. Joseph Hecht
Darwin Barney went on the DL this week spraining “the other” cruciate or Posterior Cruciate knee ligament. I’m sure the Cubs called Iowa Cubs manager Bill Dancy to let him know that his Pacific Coast League (PCL) Iowa team might shortly be getting another middle infielder on rehab assignment for his lineup. Barney sustained the injury to his right knee on the play at home plate on Monday night, scoring the Cubs only run in a 1-0 victory. It looked like he bounced his knee in the dirt during a head first dive and he did stumble a bit getting up from his dive. The MRI showed injury without stretch (grade 1) to his Posterior Cruciate Ligament (PCL). This is considered fairly minor but probably needs to be protected from further injury for about 2-3 weeks.
“As soon as I slid into home plate last night, I knew something was really wrong,” he said. “The whole knee went numb. I had an MRI today and it revealed that Grade 1 strain in my knee.” (editiorial note: ligament injuries are sprains, muscle injuries are strains)
Right now Darwin Barney can’t jump, but you can. So read more after the jump.
There has been plenty of media attention paid to the Anterior Cruciate Ligament (ACL) which when torn in a high performance athlete is treated with reconstructive surgery but little is written about in the media when the posterior cruciate ligament (PCL) is injured. The Posterior Cruciate is structurally the more robust of the two cruciates and isolated PCL injuries can occur but are less frequent and usually produce more subtle symptoms. If both the Anterior and Posterior Cruciates are torn, more drastic instability can occur including knee dislocation but fortunately that is not very common. Most people hear about the fairly common patella (kneecap) dislocation but a true knee dislocation (tibia-femur) is a severe injury and acute knee dislocations can even have nerve and artery damage.
The PCL attaches behind the knee on the tibia and goes to the medial (inner) side of the central notch on the femur. The ligament prevents posterior translation of the tibia relative to the femur above and also provides central rotational stability. Here is an excellent 3D modeling video of the PCL including how the ligament works in flexion and extension of the knee. The Anterior Cruciate (ACL) attaches to the anterior tibial spine near the front of the knee and goes to the lateral (outer) part of the femoral notch. The ligaments cross (hence, cruciate) each other and protect and stabilize the knee when working in tandem from excess rotation and translation.
Before MRI imaging was available, grade 2 vs 3 PCL injuries were sometimes subtle to diagnose on exam with what was called a “posterior sag” sign with the knee extended or a“posterior drawer” sign with the knee flexed. The PCL does image well on MRI studies (see “P” on image), so seeing injury to it (because the tissue signal is altered in injury) is straightforward making even subtle grade 1 injuries possible to diagnose these days.
The most common mechanism of injury is a direct blow to the front of the upper tibia, which is what seemed to happen to Barney’s leg in the head first dive at home plate.
Certainly, a grade 1 strain should respond to rest and rehab in a few weeks but when the PCL has a third degree injury and the knee has instability there are arthroscopically assisted surgical reconstructive techniques (see video) available. These have evolved and are significantly improved over the last 2 decades and much of the technology has been based on arthroscopic considerations for the ACL which is now a frequently performed surgery. Brewer ace Yovani Gallardo tore his ACL in May 2008 (against the Cubs avoiding contact with Prince Fielder on a Reed Johnson bunt) and was able to come back to pitch in late September and started a playoff game vs the Phillies that season. The injured PCL has better blood supply than the ACL and therefore can heal without subsequent instability. The PCL is much less frequently reconstructed (than the ACL) and often has several other associated injuries including the ACL and meniscal tears making any associated instability more extensive, so the results are more difficult to assess and should not be compared to the more common anterior cruciate ligament reconstruction outcomes. I don’t know of any major league players that have needed PCL reconstruction although I would be interested to hear if any mlb player has had this done.