Association between hip dislocation in pelvic fracture and concomitant knee ligament injuries

Acetabular fracture with concomitant hip dislocation (dislocation-fracture) is a high-energy injury requiring urgent management. Although less life-threatening than pelvic ring fractures, these injuries are often associated with ipsilateral knee trauma, which may be overlooked in the acute setting. Delayed recognition can lead to secondary meniscal and chondral damage.

To investigate whether hip dislocation in the setting of acetabular fracture is an independent risk factor for ipsilateral knee injury.

We retrospectively reviewed 180 patients (146 men, 34 women; mean age, 57.3 ± 19.8 years) admitted with acetabular fractures between July 2006 and December 2024. Clinical variables included age, sex, mechanism of injury, concomitant upper extremity injuries, initial knee evaluation, and the presence of ipsilateral knee injuries. Knee injury was defined as ligament injury, tibial plateau fracture, or meniscal injury. Notably, tibial plateau fractures that were not clearly identified on radiographs were diagnosed by MRI. Patients were stratified according to the presence of hip dislocation, and logistic regression analysis was performed to identify independent risk factors for knee injury.

Mechanisms of injury included falls (25.6 %), traffic accidents (69.4 %), and tumbling (5.0 %). Concomitant upper extremity injuries were found in 21.7 % of patients. Ipsilateral hip dislocation-fracture occurred in 46 patients (25.6 %), with directions and fracture types recorded as Thompson and Epstein classification. Knee injury was significantly more frequent in Group pH (12/46, 26.1 %) than in Group AH (5/134, 3.7 %) (P < 0.001). Logistic regression showed that age, sex, mechanism of injury, and upper extremity injuries were not independent predictors of knee or PCL injury, whereas hip dislocation-fracture significantly increased the risk (OR 7.25; 95 % CI, 2.30-22.9; P < 0.001). Among knee injuries, posterior cruciate ligament (PCL) injury was most common (41.2 %), followed by meniscal injury (17.6 %) and anterior cruciate ligament (ACL) injury (5.6 %). Concomitant tibial plateau fractures were observed in 23.5 % of cases, all confirmed by MRI. Soft-tissue-only knee injuries (ligament and/or meniscus without fracture) accounted for 10 cases.

Hip dislocation-fracture significantly increases the risk of ipsilateral knee injury, particularly PCL injury. Clinicians should maintain a high index of suspicion and perform systematic knee evaluation, including MRI when feasible, to enable early diagnosis and prevent secondary joint deterioration.