Association of Knee Ligament Injury with Pelvic and Acetabular Fractures: A Retrospective Cohort Study
This retrospective cohort study of 328 patients reveals that knee ligament injuries occur in 3.35% of pelvic or acetabular fracture cases and are significantly associated with posterior wall, combined posterior wall–column fracture patterns, and posterior hip dislocations, underscoring the need for routine knee assessments to prevent delayed diagnosis.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
When a car crash or a high fall strikes the human body with enough force to shatter the pelvis or the hip socket, the injury rarely stays contained in that one spot. The pelvis and the hip socket, known medically as the acetabulum, form a sturdy ring that supports the upper body and connects it to the legs. When this ring breaks, the energy required to cause the fracture is immense, often sending shockwaves through the entire skeleton. Because the legs are the primary point of contact in many high-impact accidents, the knees frequently absorb a portion of this violent force. While doctors are trained to look for the obvious, life-threatening breaks in the pelvic ring, the softer tissues inside the knee—specifically the strong bands of tissue called ligaments that hold the joint together—can be torn or stretched in the same instant. These hidden tears are easy to miss when a patient is in shock or has other severe injuries, yet leaving them untreated can lead to long-term pain and a permanent inability to walk normally.
A team of researchers at a major trauma hospital in Thailand set out to understand just how often these knee injuries happen alongside pelvic fractures and which specific types of breaks make a knee injury more likely. They looked back at the medical records of 328 adults who had been treated for pelvic or hip socket fractures over a ten-year period. By carefully reviewing how these patients were injured, what their scans showed, and how their knees were examined, the team sought to find a pattern that could help doctors spot these missed injuries earlier. Their work focused on the connection between the way the hip bone broke and the specific damage done to the knee's internal support structures.
The study revealed that knee ligament injuries are not rare in this group, occurring in roughly three out of every hundred patients with pelvic or hip socket fractures. While some patients had broken bones around the knee, the researchers found that the soft tissue damage was just as common. In the group of patients with ligament tears, the most frequent injury was to the posterior cruciate ligament, a key band of tissue at the back of the knee that prevents the shinbone from sliding too far backward. This specific tear happened in more than half of the ligament cases. The researchers also found that when the knee completely dislocates, it is often accompanied by a specific type of hip socket break. In fact, nearly all the patients with these knee injuries had been in a motor vehicle accident, and none had fallen from a height, suggesting that the force of a car crash is the primary driver for this combination of injuries.
The most significant finding was a clear link between the shape of the fracture and the damage to the knee. Patients who had a fracture of the back wall of the hip socket were far more likely to have a torn knee ligament than those with other types of breaks. The risk was even higher for patients whose hip socket fracture involved both the back wall and the back column of the bone. Similarly, if the hip had been dislocated backward at the time of the injury, the chance of a concurrent knee ligament tear increased significantly. The data showed that these specific fracture patterns act as a warning sign; when a doctor sees a break in the back of the hip socket, the knee on the same side is under a much higher threat of hidden damage.
Despite these clear connections, the study also highlighted how easily these injuries can be overlooked. In one instance, a patient with a torn ligament was not diagnosed until three months after the accident, long after the initial trauma had been treated. The researchers noted that the severe pain and swelling from the pelvic fracture, combined with other injuries to the head, chest, or other limbs, often distract medical teams from performing a thorough check of the knee once the patient is stable. The study found that relying solely on how a patient feels or scores on a questionnaire was not enough to catch these missed injuries; a physical examination of the knee, repeated once the patient is able to cooperate, is essential.
The authors concluded that for anyone treated for a pelvic or hip socket fracture, especially one involving the back of the socket or a backward hip dislocation, a routine and careful check of the knee is necessary. This simple step could prevent the long-term disability that comes from an undiagnosed ligament tear. While the number of patients with these specific injuries in this study was small, making the results a strong suggestion rather than a final rule, the pattern is clear enough to change how doctors approach these complex trauma cases. By paying attention to the specific way the hip breaks, medical teams can ensure that the hidden damage to the knee is not left behind.
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