Located on the outside of the knee joint, the posterolateral corner (PLC) of the knee functions to stabilize the knee against direct or, external forces. Most injuries that occur to this area are due to a sports impact, for example, football, soccer and/or basketball. Although injuries to this area of the knee represent a smaller percentage of cases compared to the ACL or MCL, the injury can create a devastating impact to athletic performance. The posterolateral corner of the knee is one of the more complex areas to both diagnose and treat surgically. Patients with posterolateral knee injuries often complain of side-to-side instability and problems with twisting, turning and pivoting. It is well recognized that injuries to this corner of the knee often initially result in minimal swelling and pain along the outside of the knee. Patients gradually note the onset of this instability pattern over ensuing weeks to months. This is problematic because the majority of patients are recommended to undergo surgery within a few weeks of the initial injury to maximize their outcome. The main anatomic structures of the posterolateral aspect of the knee are the fibular (lateral) collateral ligament (FCL), the popliteus tendon and the popliteofibular ligament. In addition, the lateral capsule is a very important stabilizer, as is the biceps femoris attachment to the fibular head. Concurrent with these ligaments it is very important to assess the function of the common peroneal nerve because the nerve crosses the fibular head very close to these structures. Approximately 15-20% of patients may have a common peroneal nerve injury who present with a posterolateral corner injury.
There are many tests which must be synthesized to diagnose a posterolateral corner knee injury. These include: • The Varus Stress Test in both full extension and at 30° of knee flexion• The Dial Test at 30° and 90° of knee flexion• The Posterolateral Drawer Test• The External Rotation Recurvatum Test, • The Reverse Pivot Shift Test • The Assessment of a Varus Thrust GaitAll these tests must be assessed in patients to determine the type of instability present. About 78% of patients who do have posterolateral knee injuries will also have a concurrent cruciate ligament injury. One must not overlook the posterolateral corner knee injury and focus only on the cruciate ligament injury because missing the posterolateral knee injury can cause failure of cruciate ligament reconstructions.Dr. LaPrade will use plain x-rays, stress x-rays, and often times, an MRI to utilize and examine the injury in each patient and to determine whether or not a posterolateral corner injury exists. In many cases, a fracture of the medial tibial plateau and of the fibular head will also present itself. Posterior knee kneeling stress x-rays should also be obtained when there is a concern for concurrent PCL tears to determine if there is any increase in posterior translation on the injuried
Posterolateral corner knee injuries are classified according to the degree of injury:• Grade I Injury: A small partial tear with minimal instability is called a grade I injury• Grade II Inury: A partial tear with an endpoint to stressing• Grade III Injury: A complete tear with no good endpoint to stressingIn general, all grade III injuries are recommended for surgery because of the low likelihood of healing for grade III posterolateral corner structures. This is primarily due to its unique anatomy where there are two convex bony surfaces present leading to inherent bony instability which results in a higher risk of having them not heal over time. In general, due to the high risk of scaring and retraction of torn structures for the posterolateral corner of the knee, it is recommended most surgeries be performed within two to three weeks after the injury to allow for early range of motion and to make sure sutures can easily be held into the torn structures.
Dr. LaPrade usually recommends a combined hybrid approach of repair for repairable structures and an anatomic a reconstruction of midsubstance tears of the posterolateral corner in acute injuries; while in chronic injuries he will generally perform anatomic reconstructions. Dr. LaPrade has developed multiple surgical techniques to treat these injuries to include fibular collateral ligament reconstructions, popliteus tendon reconstructions, proximal tibiofibular joint reconstructions, and complete posterolateral corner reconstructions. All of these procedures have proven to result in positive patient outcomes.
The postoperative rehabilitation for these injuries includes a limited range of motion within the “safe zone” decided by Dr. LaPrade as he moves the knee and assesses the stress on the repaired structures at the time of surgery, to be nonweight bearing for six weeks postoperatively and to avoid isolated active hamstring exercises for the first four months postoperatively to avoid significant stress to the healing posterolateral corner repair and reconstruction procedures.
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