Terminology is important in orthopaedics. When teaching, for instance, we stress the need for trainees to be able to articulate what a radiograph is showing using descriptive terms and classification systems.
Over the years, “multiligamentous knee injury” (MLKI) and “knee dislocation” have increasingly been used interchangeably within the orthopaedic vernacular, in part because of the high energy required to sustain such injuries, but also because of the potentially devastating complications that can be associated with both.
Kahan et al. sought to better characterize these injuries and their associated complications in a study now reported JBJS. They retrospectively evaluated cases treated at their Level-I trauma center between 2001 and 2020.
A total of 123 patients with MLKI were included in the analysis: 45 patients with and 78 patients without a documented knee dislocation. MLKI was defined as disruption of at least 2 of the following: the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments. Cruciate ligament injuries and isolated injuries of the superficial medial collateral ligament were not included unless there was disruption of the posteromedial corner, semimembranosus, or medial patellofemoral ligament, indicating a more extensive medial-sided injury.
The investigators found that medial-sided injuries were more common in the dislocation group (53% vs 30%; p = 0.009), and the dislocation group had higher rates of peroneal nerve injury (38% vs 14%; p = 0.004) and vascular injury (18% vs 4%; p = 0.018). Of the 11 total patients with a vascular injury, 8 (73%) were in the dislocation group; 10 of the 11 underwent a vascular surgical procedure.
Not all cases of MLKI are a result of a knee dislocation, and in this adequately powered study, there were differences in the injury pattern and associated injuries between those with and without true dislocation. It is important to note that, although higher rates of neurovascular injury were seen in the dislocation group, such events also occurred in the group without dislocation, so a high index of suspicion must be maintained with these complex injuries. As the authors suggest, it may be better to consider cases of knee dislocation a subset of MLKI with the potential for increased neurovascular compromise.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
You know you’re having a bad day at the gym when both your knees dislocate during a leg-press workout. That is what happened to a 44-year-old male recreational weight lifter who “locked out” both his knees while trying to press 1,100 lbs. This unusual case is described in the latest issue of JBJS Case Connector.
Knee joint dislocations are true emergencies because of the potential for concomitant neurovascular injury. This patient was transferred to a tertiary academic hospital for emergency closed reduction and application of knee-spanning external fixators. Although both tibiae were dislocated anteriorly, both lower extremities were neurovascularly intact.
One month after the initial injury, the external fixators were removed and the knees were placed in bilateral hinged braces. MRI performed shortly thereafter revealed tears of multiple ligaments and distal popliteus tendon tears in both knees. At 4 months postinjury, the patient underwent left-side ACL reconstruction, PCL reconstruction, FCL repair and reconstruction, popliteal reconstruction with allograft, and a popliteofibular ligament reconstruction. Seven months after that, he underwent similar procedures on the right side.
At the most recent postsurgical follow-up, 17 months after the initial injury, the range of motion in both knees was 0° to 130°, and the patient was able to participate in straight line running, squats, and cycling.
The authors emphasize that any locking of the knees results in 5° to 10° of hyperextension, which places an increased load across the ACL. Add to that the heavy weight and the abrupt increase in velocity at the extreme range of motion, and you have a recipe for serious injury. The authors conclude that “the risk of knee dislocation can be reduced by avoiding locking and hyperextension of the knees during any type of leg press or squatting exercise.”
For more information about JBJS Case Connector, watch this video featuring JBJS Editor in Chief Dr. Marc Swiontkowski.