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.
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.
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.
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.
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 jbjs.org (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.
1. . The incidence and pattern of knee injury associated with dislocation of the hip. J Bone Joint Surg Br. 1975;57: 376-8.
2. , Truan JR. Knee injuries in traumatic hip dislocation. Clin Orthop Relat Res. 2000;377: 78-83.
3. , Davidson M, MacDonald PB, Froese W, Sutherland K. The efficacy of magnetic resonance imaging in acute knee injuries. Clin J Sport Med. 2000;10: 34-9.
4. , Li KC, Hollett MD, Bergman AG, Herfkens RJ. Meniscal tears of the knee: accuracy of detection with fast spin-echo MR imaging and arthroscopic correlation in 293 patients. Radiology. 1997;203: 508-12.
5. , Watkinson AF, Ackroyd CE, Johnson C. Magnetic resonance imaging of meniscal and cruciate injuries of the knee. J Bone Joint Surg Br. 1991;73: 452-7.
6. , Stoller DW. The menisici. In: Mink JH, Crues JV, Reicher MA, editors. Magnetic resonance imaging of the knee. 2nd ed. New York: Raven Press; 1993. p 96-114.
7. , Marks PH, Fowler PJ, Munro TG. Occult posttraumatic osteochondral lesions of the knee: prevalence, classification, and short-term sequelae evaluated with MR imaging. Radiology. 1991;178: 271-6.
8. , Galland MW, Barrack RL, Neitzschman HR, Harris MB, Myers L, Vrahas MS. Magnetic resonance imaging of the knee after ipsilateral femur fracture. J Orthop Trauma. 2002;16: 567-71.
9. , Johnson DL. Subchondral contusion of the knee caused by axial loading from dashboard impact: detection by magnetic resonance imaging. J South Orthop Assoc. 2000;9: 13-8.
10. , Kathrein A, Freund MC, Klestil T, Kreczy A. Bone bruise of the knee: histology and cryosections in 5 cases. Acta Orthop Scand. 1998;69: 291-4.
11. , Osborne JR, Gordon WT, Hinkin DT, Brinker MR. The natural history of bone bruises. A prospective study of magnetic resonance imaging-detected trabecular microfractures in patients with isolated medial collateral ligament injuries. Am J Sports Med. 1998;26: 15-9.
12. , Noonan K, Kayes K. “Bone bruises” of the knee: a review. Iowa Orthop J. 1998;18: 112-7.
13. , Dupuy DE, Siliski JM. Comparison of magnetic resonance imaging with operative findings in acute traumatic dislocations of the adult knee. J Orthop Trauma. 2000;14: 183-6.
14. , Letsch R, Turowski B. Which factors influence the progression of degenerative osteoarthritis after ACL surgery? Knee Surg Sports Traumatol Arthrosc. 1994;2: 80-4.
15. , Messner K. Eighteen- to twenty-four-year follow-up after complete rupture of the anterior cruciate ligament. Am J Sports Med. 1999;27: 711-7.
16. , Roos EM, Roos H. High presvalence of osteoarthritis 14 years after an anterior cruciate ligament tear in male soccer players: a study of radiographic and patient relevant outcomes. Ann Rheum Dis. 2004;63: 269-73.
17. , Papadonikolakis A, Moebius UG, Gelalis I, Motsis E, Soucacos PN. Posterior tibial subluxation and short-term arthritis resulting from failed posterior cruciate ligament reconstruction. Arthroscopy. 2003;19: E43.
18. , Subcommittee on Classification of Sports Injuries and Committee on the Medical Aspects of Sports. Standard nomenclature of athletic injuries. Chicago: American Medical Association; 1968. p 99-100.Copyright 2005 by The Journal of Bone and Joint Surgery, Incorporated