Dislocation of the knee and vascular injury
Knee dislocation makes up less than 0.5% of joint dislocations and less than 0.2% of all orthopaedic injuries, 1,2, but between 22% and 32% of patients with acute knee dislocation can have a devastating complication such as vascular injury and in most cases arteria poplitea is affected. 3,4 This is the reason why the case presented by Seewoonarain and Servant is extremely useful for clinical practice.5
According to the authors, these injuries may be missed or underestimated and they must be carefully reviewed with any imaging modalities used.
It is also important that arteria poplitea injury is not missed or underestimated when it is found. The physical examination findings can be misleading and alone may fail to identify significant vascular injury. 6
Medina et al. report that the best method for evaluating vascular injury in patients with knee dislocation is not very clear, but in 90% of cases the preferred method is angiography.7
Popliteal artery injury can be detected noninvasively by measuring systolic blood pressure and defining the ankle-brachial index (ABI). Originally described by Winsor, ABI is the ratio of the systolic blood pressure measured at the ankle to that measured at the brachial artery.8 Mills et al. state a 100% predictive value of an ABI lower than 0.90 in patients with knee dislocation and arteria poplitea injury. 9 ABI’s rate according to Levy et al. requires subsequent vascular assessment with either Duplex ultrasonography or angiography. 10
1. Richter M, Lobenhoffer P, Tscherne H. Knee dislocation. Longterm results after operative treatment. Chirurgia 1999;70: 1294—301
2. Robertson A, Nutton RW, Keating JF. Dislocation of the knee. J Bone Joint Surg [Br] 2006;88-B:706-11.
3. Green NE, Allen BL. Vascular injuries associated with dislocation of the knee. J Bone Joint Surg Am. 1977;59:236–239.
4. Wascher DC, Dvirnak PC, DeCoster TA. Knee dislocation: initial assessment and implications for treatment. J Orthop Trauma. 1997;11:525–529.
5. Seewoonarain S Servant C. A painful swollen knee after a fall BMJ 2017; 356: i6772 doi: 10.1136/bmj.i6772
6. McDonough EB Jr, Wojtys EM. Multiligamentous injuries of the knee and associated vascular injuries. Am J Sports Med. 2009;37:156–159.
7. Medina O, Arom GA, Yeranosian MG, Petrigliano FA, McAllister DR Vascular and nerve injury after knee dislocation: a systematic review. Clin Orthop Relat Res. 2014 Sep;472(9):2621-9.
8. Winsor T. Influence of arterial disease on the systolic blood pressure gradients of the extremity. Am J Med Sci. 1950; 220:117–126.
9. Mills WJ, Barei DP, McNair P.The value of the ankle-brachial index for diagnosing arterial injury after knee dislocation: a prospective study. J Trauma. 2004 Jun;56(6):1261-5.
10. Levy BA, Krych AJ, Shah JP, Morgan JA, Stuart MJ. Staged protocol for initial management of the dislocated knee. Knee Surg Sports Traumatol Arthrosc. 2010;18:1630–1637.
Competing interests: No competing interests