Acta Orthop. Belg., 2004, 70, 498-501 CASE REPORT

Spontaneous non-traumatic dislocation of the

Alistair PACE, Colin FERGUSSON

From the Royal Berkshire Hospital, Reading, U.K.

Ligamentous injuries of the knee occur during sports In the emergency department closed reduction and where there is extensive injury associated with was performed and post-reduction films were nor- or dislocation. We present a case of an mal (fig 2). The vascular and sensory deficit did not obese female who sustained spontaneous non-trau- improve. An angiogram was performed and this matic posterior knee dislocation when she caught her was normal. Subsequently an M.R.I. showed a while rising from the sitting down position. gross knee effusion and bone oedema. The anterior There was associated peroneal nerve injury but an angiogram confirmed no vascular compromise. cruciate was completely disrupted and the Surgical ligamentous reconstruction was under- posterior cruciate ligament appeared irregular indi- taken. cating a partial tear. The medial collateral ligament showed a high signal indicating a but there was a complete disruption of the lateral collateral ligament complex and the postero-lateral corner of CASE HISTORY the knee. The menisci appeared normal. The patient subsequently underwent a hamstring A 22-year-old obese non-diabetic female reconstruction of her ruptured A.C.L. The lateral (weight : 120 kg ; height : 162 cm) was sitting on a collateral ligament complex, postero-lateral corner couch when on standing up she caught her left foot and posterior capsule were also reconstructed. The on the carpet and twisted her knee. She subse- knee was placed in a full leg cast following which quently fell to the ground with severe pain. There a genu-range brace was used allowing 20-80¡ flexi- was immediate deformity of the knee. On examina- on. There were no vascular complications in the tion in the emergency department a left knee dislo- limb during or after the procedure. cation was identified. The left dorsalis pedis pulse was present but there was no tibialis posterior pulse. There was no motor dysfunction in her left foot but there was decreased sensation in the com- ■ Alistair Pace, MD, MRCS (Eng.), MRCS (Ed.), mon peroneal nerve distribution over her left leg. Specialist Registrar Trauma and Orthopaedics. was limited by pain and ■ Colin Fergusson, MA, FRCS. Consultant Orthopaedic swelling. There was no evidence of hyperlaxity. Surgeon. There were no other medical problems and there Department of Trauma and Orthopaedics, Royal Berkshire Hospital, Reading, U.K. was no previous history of knee injury or pain. Correspondence : Alistair Pace, Flat 20, Millcroft Park 322, Anterior-posterior and lateral radiographs con- Frankby Road Greasby Wirral CH49 3PE, U.K. firmed posteromedial knee dislocation and no evi- E-mail : [email protected]. dence of osteoarthritis (fig 1). © 2004, Acta Orthopædica Belgica.

Acta Orthopædica Belgica, Vol. 70 - 5 - 2004 SPONTANEOUS NON-TRAUMATIC DISLOCATION OF THE KNEE 499

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Fig. 1a, b. — Anteroposterior and lateral radiographs showing the left knee in posterior dislocation

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Fig. 2a, b. — Anteroposterior and lateral radiographs showing the left knee joint after reduction

DISCUSSION paedic emergencies. It can be disabling if immedi- ate recognition and treatment are delayed. The Complete knee dislocation is a rare severe injury injury may present as frank dislocation, a knee that and usually follows high energy trauma during is dislocatable under anaesthesia or a pattern of soft contact sports, traffic accidents, or falls from great tissue injury which suggests spontaneously reduc- heights. It represents one of the few true ortho- ed dislocation (4). Knee dislocation may be classi-

Acta Orthopædica Belgica, Vol. 70 - 5 - 2004 500 A. PACE, C. FERGUSSON fied according to the position of the relative to injuries in complex knee disruptions. It also pro- the as anterior (31%) due to hyperextensive vides information which is useful in pre-operative forces, posterior (25%) due to direct anterior trau- evaluation and planning, including availability of ma, medial and lateral due to severe valgus and allograft. It is helpful to limit the potentially dis- varus angulation. Postero-lateral dislocation fol- abling sequellae of knee dislocations. It is especial- lows a marked valgus stress and internal tibial rota- ly useful when physical examination is limited by tion causing the medial femoral condyle to button- pain and swelling (2). hole through the antero-medial capsule. A large However false negatives with lateral collateral number of unspecified dislocations are documented ligament tears and postero-lateral capsule disrup- reflecting the tendency towards spontaneous reduc- tions have been described. tion and hence in knee injuries a high degree of Most knee dislocations are associated with rup- suspicion of such spontaneous dislocation must be ture or avulsion of both cruciates, with collateral kept in mind (1). ligament ruptures and meniscal tears. An injury to Complete knee dislocation of the non-contact the popliteal tendon seems to indicate a more type is exceedingly rare. In this case severe over- severe mechanism of trauma resulting from poste- weight appears to be the principal cause of the rior or postero-lateral dislocation. In this case the complete knee dislocation. P.C.L. was intact even though there was a complete Most dislocations are associated with intra-artic- tibiofemoral dislocation. Such cases usually suffer ular and extra-articular ligamentous injury as well valgus-varus instability due to accompanying dis- as capsular, vascular and nerve injury (10). Nerve ruption of the collateral . injuries mostly related to the common peroneal Non-operative treatment with casting of knee nerve, are reported in 4.8% of low velocity knee dislocation has been shown to yield mixed results dislocations. Vascular injury occurs in the range of with some patients having residual disabling laxi- 16% to 60% (8). Other complications include liga- ty : 69% reported good results but 30% reported mentous instability, stiffness, persisting pain and instability (5). Acute operative repair of multiple ultimately degenerative disease. Major concerns in ligamentous injuries can provide better knee treating knee dislocations are the immediate assess- stability but frequently causes permanent stiffness : ment of neurovascular integrity as well as ligamen- 43% report achieving less than 90¡ of movement. tous stability. Popliteal vessel injuries can result in However repair allows stability and early protected and a delay of vascular repair of more mobilisation and is rewarding (9). than 8 hours results in 85% amputation rate (3). In In this case report it is our view that the patient anterior dislocation the popliteal bowstrings put tremendous stress on her knee joint at a parti- over the back of the femoral condyle and in poste- cular moment as the result of severe overweight. rior dislocation there is an increased risk of lacera- Morrison and Arden (7) have shown that the magni- tion and rupture of the artery. It must be empha- tude of the joint reaction force is two to four times sised that there may be an occult vascular injury the body weight and if the muscles and ligaments due to intimal tears with normal distal pulses and cannot sustain the enormous forces on the joint, the hence an angiogram should be performed immedi- knee subsequently becomes unstable, collapses and ately (6, 11). Nerve injuries due to traction and direct dislocates. trauma may result in neurapraxia, axonotmesis and neurotmesis ; most of these injuries result in neura- praxia, they do not require intervention and recover REFERENCES within 3 months. Their recovery may be followed up by electromyography. If there is complete palsy 1. Brautigan B, Johnson DL. The epidemiology of knee dis- locations. Clin Sports Med 2000 ; 19 : 387-397. at the outset, prognosis for recovery is dismal. 2. Chen VW, Anderson K. Reconstruction of the anterior MRI scanning is useful and provides objective and posterior cruciate ligaments after recurrent anterior and accurate (85%-100%) diagnosis of soft tissue knee dislocation. J Knee Surg 2003 ; 16 : 179-181.

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3. Durbhakula SM, Das SP. Traumatic anterior knee dislo- 8. Putukian M, McKeag D. Non-contact knee dislocation in cation. Orthopedics 2002 ; 25 : 1083-1085. a female basketball player : a case report. Clin J Sport Med 4. Good L, Johnson RJ. The dislocated knee. J Am Acad 1995 ; 5 : 258-261. Orthop Surg 1995 ; 3 : 284-292. 9. Richter M, Bosch U. Comparison of surgical repair or 5. Liow RY, McNicholas MJ. Ligament repair and recon- reconstruction of the cruciate ligaments versus non surgi- struction in traumatic dislocation of the knee. J Bone Joint cal treatment in patients with traumatic knee dislocations. Surg 2003 ; 85-B : 845-851. Am J Sports Med 2002 ; 30 : 718-727. 6. Martinez D, Sweatman K, Thompson EC. Popliteal 10. Rios A, Villa A. Results after treatment of traumatic knee artery injury associated with knee dislocation. Am Surg dislocations : report of 26 cases. J Trauma 2003 ; 55 : 489- 2001 ; 67 : 165-167. 494. 7. Morrison WJ, Arden GP. Traumatic dislocation of the 11. Wascher DC. High velocity knee dislocation with vascu- knee : a report of 43 cases. J Bone Joint Surg 1972 ; 54-B : lar injury. Treatment principles. Clin Sports Med 2000 ; 96-102. 19 : 479-492.

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