Knee Injury in Patients Experiencing a High-Energy Traumatic Ipsilateral Hip Dislocation

Schmidt, Gary L. MD; Sciulli, Robert MD; Altman, Gregory T. MD

Journal of Bone & Joint Surgery - American Volume: June 2005 - Volume 87 - Issue 6 - p 1200–1204
doi: 10.2106/JBJS.D.02306
Scientific Articles

Background: Traumatic hip dislocation results from the dissipation of a large amount of energy about the hip joint. Clinically, these forces often are first transmitted through the knee en route to the hip. It is therefore logical to look for coexistent ipsilateral knee injury in patients with a traumatic hip dislocation.

Methods: Over a one-year period, we prospectively evaluated the ipsilateral knee of all patients who had a traumatic hip dislocation on the basis of a standardized history, physical examination, and magnetic resonance imaging.

Results: Twenty-one (75%) of the twenty-eight knees were painful. Twenty-five (89%) of the twenty-eight knees had visible evidence of soft-tissue injury on inspection. Magnetic resonance imaging revealed evidence of some abnormality in twenty-five (93%) of twenty-seven knees, with effusion (37%), bone bruise (33%), and meniscal tear (30%) being the most common findings.

Conclusions: The present study provides evidence of a high rate of associated ipsilateral knee injuries in patients with a traumatic hip dislocation. Bone bruises may provide a plausible explanation for persistent knee pain following a traumatic hip dislocation. The liberal use of magnetic resonance imaging is recommended for the evaluation of these patients in order to detect injuries that may not be discoverable on the basis of a history and physical examination alone.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

1 Departments of Radiology (R.S.) and Orthopaedic Surgery (G.T.A.), Allegheny General Hospital, 320 East North Avenue, Pittsburgh, PA 15212

2 531 Perry Highway, Apartment #11, Pittsburgh, PA 15229. E-mail address:

Article Outline

Traumatic hip dislocation results from the dissipation of large physical forces about the hip joint. In many instances, this energy is first transmitted through the knee en route to the hip. However, little has been reported about associated knee injuries in patients with a traumatic hip dislocation1,2. Both Gillespie1 and Tabuenca and Truan2 reported a high rate of knee injury among patients who also had a hip dislocation. Those authors recommended the performance of a thorough physical examination in order to identify knee abnormalities early and hence to optimize functional outcome.

Physical examination of the ipsilateral knee in patients who have recently experienced a hip dislocation is often difficult. Limited range of motion of the hip, referred pain to the knee from the hip, generalized discomfort, muscular spasms with resultant guarding, and the use of braces such as an abduction pillow all serve to impede a complete and thorough examination of the ligaments of the ipsilateral knee. Magnetic resonance imaging has been shown to be both sensitive and specific for demonstrating intra-articular abnormalities about the knee3-5. To better define the extent and severity of knee injury, we prospectively evaluated the ipsilateral knee in all patients with a traumatic hip dislocation on the basis of a history, physical examination, and magnetic resonance imaging.

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Materials and Methods

The present study involved a prospective evaluation of all patients who were eighteen years of age or older and who presented to a level-I trauma center in a major metropolitan area with a traumatic hip dislocation over a one-year period. Exclusion criteria included any previous hip surgery, a previous hip dislocation, an age of less than eighteen years, or an inability to undergo magnetic resonance imaging (e.g., because of retained metal fragments, a pacemaker, or pregnancy). The study was approved by the institutional review board. Informed consent was obtained from all participating patients. All participants underwent a standardized history and physical examination of the ipsilateral knee, which included a complete ligamentous, meniscal, patellar, and soft-tissue evaluation. The physical examination was performed preoperatively for every patient by one experienced attending surgeon (G.T.A.) who was fellowship-trained in both sports medicine and orthopaedic trauma. Often, this examination was difficult and/or limited because of patient discomfort and an inability to cooperate because of the hip injury. All patients who subsequently were taken to the operating room for acetabular surgery also underwent a complete knee examination under anesthesia at the conclusion of surgery. A detailed list of all components of the physical examination is included in the Appendix. In addition, all patients underwent magnetic resonance imaging of the same knee at the earliest convenient time during the period of hospitalization. Twenty-eight patients met the criteria for inclusion in the study, and twenty-seven patients (twenty-eight hips) elected to enroll. The prevalence of knee abnormalities associated with ipsilateral hip dislocation was thus determined on the basis of the history, physical examination, and magnetic resonance imaging findings. One patient who was included in the study had had a previous ipsilateral total knee arthroplasty. The magnetic resonance imaging findings for this patient are not included because metallic artifact precluded meaningful interpretation of the study.

All magnetic resonance imaging studies were performed with use of a 1.5-T Siemens Symphony magnet (Siemens, Iselin, New Jersey) and a dedicated extremity coil. Magnetic resonance imaging studies were interpreted by two musculoskeletal radiologists (including one of the authors [R.S.]) who were blinded with regard to the clinical history and physical findings. Meniscal tears were classified according to the system described by Crues and Stoller6 in an attempt to differentiate between acute and chronic tears. Bone bruises were categorized according to the system described by Vellet et al.7.

At the conclusion of the study, we undertook an ad hoc follow-up evaluation of all patients who had evidence of cruciate ligament injury on the magnetic resonance imaging scan.

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Patient Characteristics

Patient characteristics are presented in Table I. Twenty-one (75%) of the twenty-eight ipsilateral knees were painful.

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Physical Examination

Eleven (39%) of the twenty-eight knees were unable to undergo a complete physical examination. Physical examination revealed that only two (7%) of the twenty-eight knees had evidence of an injury involving a major knee ligament (either cruciate or collateral ligament). Despite this finding, ten knees (36%) had clinical evidence of an effusion. Four knees (14%) had evidence of potential meniscal injury (either a positive McMurray test or joint-line tenderness). Twenty-five knees (89%) had visible evidence of soft-tissue injury (abrasion, ecchymosis, contusion, or laceration) on inspection.

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Hip Dislocation Characteristics

Twenty-four (86%) of the twenty-eight hip dislocations were posterior, three were anterior, and one was intrapelvic (protrusio). Twenty-two patients had sustained an acetabular fracture at the time of the hip dislocation (Table II). All of the acetabular fractures required surgical stabilization in order to maintain hip stability. Fourteen dislocations occurred on the left side, and fourteen occurred on the right.

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Magnetic Resonance Imaging Evaluation

Magnetic resonance imaging demonstrated evidence of some abnormality in twenty-five (93%) of twenty-seven knees. Seven cruciate ligament injuries were detected. Five of these injuries involved the posterior cruciate ligament; these injuries included detachment of the ligament from its tibial insertion site (two knees), a midsubstance tear (one), intrasubstance signal changes (one), and a tibial plateau fracture that extended into the insertion site (one). Six collateral ligament injuries were found. Magnetic resonance imaging demonstrated an effusion in ten knees (37%), an extensor mechanism rupture in two (7%), and a periarticular fracture in four (15%).

Eight meniscal tears were found. According to the system of Crues and Stoller6, one tear was classified as grade I and one was classified as grade II. The remaining tears were classified as grade III (with signal changes extending to the articular surface), indicating evidence of acute pathology. Hence, six knees (22%) showed an acute meniscal tear.

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Bone bruises or evidence of marrow edema were found in nine knees (33%). According to the system of Vellet et al.7, all of these lesions were categorized as reticulated bone bruises, except for one that was associated with evidence of impaction. One bone bruise involved the patella; three, the medial femoral condyle; three, the anterior aspect of the tibial plateau; and one, the lateral femoral condyle. There was no evidence of marrow edema in the femoral trochlea in any patient.

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Cruciate Ligament Injury

The six patients who had evidence of cruciate ligament injury on magnetic resonance imaging were contacted for a follow-up evaluation. The mean duration of follow-up was eleven months. Five patients underwent a physical examination of the knee, and one was contacted only by telephone. Two patients complained of persistent knee instability, and one patient complained of knee stiffness. Of the five knees that were examined, three were stable. Of the remaining two knees, one had 2+ anterior instability and 2+ posterior instability and the other had a decreased range of motion (from 20° to 80°). None of these patients had undergone surgery on the ipsilateral knee or had any intention of doing so in the near future.

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In the present study, the majority of patients who had sustained a traumatic hip dislocation complained of ipsilateral knee pain but fewer than one-third of the knees had evidence of intra-articular abnormalities on physical examination. Given the high (89%) prevalence of visible soft-tissue injury on inspection, it was apparent that these knees had sustained substantial injury that could be responsible for the intraarticular abnormalities. These findings are similar to those described by Tabuenca and Truan2, who, in a study of forty-six patients with a traumatic hip dislocation, reported that seven patients had a delayed diagnosis of clinically important knee injuries (most commonly, partial or complete rupture of the anterior or posterior cruciate ligament). In a retrospective review of medical records, Gillespie1 reported thirty-five ipsilateral knee injuries among 135 patients with a posterior hip dislocation. Twenty-five of these injuries were osseous fractures or osteochondral lesions. This is in contrast to the findings in our study, in which periarticular fractures occurred in 14% of the knees whereas ligamentous injuries were more commonly detected via magnetic resonance imaging.

The vast majority of the injuries in the present study were the result of a motor-vehicle accident. The posterior cruciate ligament injuries provided evidence of a posteriorly directed force on the knee (as would be expected in association with a dashboard injury) (Figs. 1-A and 1-B). Other authors8 have reported a substantial prevalence of knee injuries on magnetic resonance imaging after ipsilateral femoral fracture; it is likely that these knee injuries occurred through a mechanism similar to that described in the present study.

Examination with the patient under anesthesia comprises an important part of the diagnostic workup of any trauma patient who is unable to cooperate fully with an examination performed while he or she is awake. This is especially true in the case of a patient who has sustained an ipsilateral hip dislocation. Unfortunately, examination with the patient under anesthesia will not detect bone bruises and may miss some other injuries such as a meniscal tear, a partial ligament disruption, or an extensor mechanism injury. In the present series, we detected two extensor mechanism injuries on the basis of magnetic resonance imaging. Both were partial tears that did not require operative repair. Some of the injuries that can be detected with magnetic resonance imaging (including cruciate ligament tears and meniscal tears) are not expected to heal with nonoperative treatment alone and may require more aggressive therapeutic intervention.

The majority of the meniscal findings in the present series were grade-III injuries. This finding is consistent with acute traumatic injury rather than chronic pathology. Again, it appears that the ipsilateral knee incurred damage during the initial traumatic episode that also resulted in the hip dislocation.

The finding of bone bruises in 33% of the knees is interesting for several reasons (Fig. 2). These results are similar to those reported by Bealle and Johnson9, who reported that magnetic resonance imaging demonstrated bone bruises in eight of twenty-one knees among patients who had an ipsilateral acetabular fracture and/or hip dislocation. In addition, our findings provide direct evidence of substantial forces being applied directly to the ipsilateral knee. Rangger et al.10 showed that the marrow edema pattern of a bone bruise is histologically consistent with the findings of subchondral microfracture. The natural history of such bone bruises has been discussed in the literature by various authors11,12. While these bruises appear to resolve with time, they can conceptually provide a practical reason for persistent knee pain following hip dislocation. The pattern of primarily reticulated lesions would seem to indicate that patients with these bruises are not at an increased risk of degenerative disease according to the system of Vellet et al.7. The anatomic location of the bone bruises may lend some credence to an injury mechanism of a flexed knee striking a dashboard. The patella, the anterior part of the tibia, and the medial femoral condyle were the most commonly involved sites. So-called “kissing” lesions, as may occur in association with a varus or valgus-type impaction injury, were not seen.

One may question the clinical importance of certain magnetic resonance imaging findings. Lonner and colleagues13 showed that clinical examination with the patient under anesthesia is more accurate than magnetic resonance imaging is for the detection of intra-articular pathology following a knee dislocation. The importance of intrasubstance signal abnormalities is unknown. Clinical instability as defined by examination with the patient under anesthesia always takes precedence in determining treatment. However, these sub-clinical findings may result in long-term functional effects or the development of osteoarthritis. Kullmer et al.14 showed a correlation between osteoarthritic changes and anterior cruciate ligament injury that was irrespective of the grade of cruciate ligament instability. The association between anterior cruciate ligament injury and osteoarthritis has been reported in the literature15,16, and Maletius and Messner15 reported that forty-seven (84%) of fifty-six patients had radiographic evidence of osteoarthritis after twenty years of follow-up. Von Porat et al.16 also reported a high prevalence of osteoarthritis in male soccer players fourteen years after anterior cruciate ligament disruption. Mavrodontidis et al.17 reported the development of arthritis after failed posterior cruciate ligament reconstruction.

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Study Limitations

The primary limitation of the present study was that these patients did not have long-term follow-up, which would have allowed us to obtain data on the functional outcomes for the affected knees. It would have been educational to learn the natural history of the injuries that we detected and to determine how many patients underwent knee surgery. If all of the patients could have undergone arthroscopy for definitive diagnosis, we would have had a gold standard with which we could have calculated the sensitivity and specificity of both physical examination and magnetic resonance imaging for the detection of knee injury in these patients. Longer-term follow-up also would have allowed us to determine if the magnetic resonance imaging findings led to subsequent changes in patient management. In addition, long-term studies are needed in order to determine whether injury to the cruciate or collateral ligament does in fact lead to the development of osteoarthritis. We did attempt to obtain limited follow-up data on the cruciate ligament injuries that were detected with magnetic resonance imaging, and we did identify abnormalities in two of six knees.

Given the difficulty of obtaining a complete physical examination of a patient who has had a hip dislocation, we recommend the liberal use of magnetic resonance imaging for the detection of associated knee abnormalities. The importance of the magnetic resonance imaging findings is not always clear, but these findings can add valuable information to the entire clinical picture. Because these patients are unable to walk for three months, knee instability or other pathological changes may otherwise not become apparent for six to twelve months after the injury, when the patients do become more active.

In summary, the present prospective evaluation of a consecutive series of patients with a hip dislocation showed a high prevalence of associated knee injuries. A thorough evaluation of the ipsilateral knee on the basis of a history and physical examination must be performed in all cases. Furthermore, on the basis of the results of the present study, we recommend the liberal use of magnetic resonance imaging for the evaluation of these patients. By defining injuries early, appropriate treatments can be more rapidly initiated, thus hopefully leading to improved functional outcomes.

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Tables presenting the physical examination components and the magnetic resonance imaging findings on all patients are available with the electronic versions of this article, on our web site at (go to the article citation and click on “Supplementary Material”) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM). ▪

Investigation performed at the Departments of Radiology and Orthopaedic Surgery, Allegheny General Hospital, Pittsburgh, Pennsylvania

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from The Pittsburgh Foundation. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

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