posterolateral rotary knee dislocation is a rare orthopedic injury that is considered to be irreducible by closed reduction because of soft tissue incarceration . here ,
we present a case of posterolateral rotary knee dislocation , which was reduced by closed manipulation .
the patientwas a 33-year - old man who sustained a twisting injury to his right knee that was diagnosed as posterolateral rotary knee dislocation by plain radiographs and the characteristic physical finding known as a dimple sign . under general anesthesia ,
the knee dislocation was reduced by closed manipulation with internal rotation of the lower leg at knee flexion and reproduced by valgus and external rotation stress .
there were was complete tear of posterior cruciate ligament , and partial tear of the anterior cruciate ligament which were not reconstructed .
one year postoperatively , the range of motion was 0145. there was no knee symptom and no ligament instability .
dislocation of the knee is a serious but rare injury , representing less than 0.2% of all orthopedic injuries .
posterolateral rotary dislocation is much rarer and considered to be irreducible by closed reduction because of incarceration of soft tissues such as the medial capsule and retinaculum , vastusmedialis , and medial meniscus .
the dimple sign is a physical finding caused by invagination of the skin and soft tissues into the medial joint space and is known to be characteristic of irreducible knee dislocation . to the best of our knowledge ,
there has been no reported case of posterolateral rotary knee dislocation successfully reduced by closed manipulation . here ,
we present a case of posterolateral rotary knee dislocation with a clear dimple sign , which was reduced using a closed procedure .
we believe that this is the first report of a successful closed reduction for posterolateral knee dislocation .
a 33-year - old man presented to the emergency department of our hospital with a twisting injury to his right knee and an open fracture of the left lower thigh that occurred while he was operating a rotary snow removal vehicle and his left lower thigh became trapped in the rotary blade .
physical examination revealed that the right knee joint was fixed at 30 flexion with a lateral shift of the patella .
radiographic evaluation confirmed lateral dislocation of the patella and posterolateral subluxation of the knee ( fig .
radiographs showing lateral dislocation of the patella and posterolateral subluxation of the tibia . on the day of injury ,
the open fracture of the left lower thigh was stabilized with an external fixator after debridement and the dislocated patella of the right knee was reduced .
plain radiographs after manipulation showed widening of the medial joint space and tibial posterolateral displacement ( fig .
( a ) anteroposterior and ( b ) lateral radiographs after reduction of the patella .
invagination of the skin over the medial joint line ( arrow heads ) is shown ( dimple sign ) .
the knee was flexed to 120 and valgus stress and internal rotation of the lower thigh were applied .
after reduction , ligament instability tests were positive for valgus stress , with signs of posterior sagging in the posterior drawer test , and negative for the lachman test , pivot shift test , extension recurvatum test , and dial test .
a subsequent arthroscopic examination also revealed a complete midsubstance tear of the posterior cruciate ligament ( pcl ) ( fig .
4a ) and a partial tear of the posterolateral bundle of the anterior cruciate ligament ( acl ) , which were not reconstructed ( fig .
a peripheral longitudinal tear of the lateral meniscus was repaired using the fast fix 360 meniscal repair system ( smith & nephew , andover , ma , usa ) ( fig .
( c ) a peripheral longitudinal tear of the lateral meniscus was repaired using the fast fix360 meniscal repair system .
thereafter , a 7-cm medial longitudinal incision was made to repair the medial collateral ligament ( mcl ) .
the medial retinaculum and capsule were torn along with the distal end of the vastusmedialis .
button holing of the medial femoral condyle through the medial retinaculum and the capsule could be reproduced by valgus stress and external rotation in the knee flexion position ( fig .
in addition , the dislocation could be reduced by internal rotation of the lower thigh .
the mcl was fixed to the femoral footprint using suture anchors ( mitek products , johnson & johnson company , westwood , ma , usa ) .
range of motion ( rom ) exercises was started after 3 weeks of immobilization with a cylinder cast .
one year postoperatively , no knee symptoms were observed and the rom was 0145. there was no ligament instability except for the pcl at grade ii .
( a ) the medial retinaculum and capsule were torn along with the distal end of the vastusmedialis .
( b ) buttonholing of the medial femoral condyle was reproduced by valgus stress and external rotation at the knee flexion position .
the most effective mechanism for posterolateral knee dislocation is considered valgus and rotational stress during knee flexion .
however , the direction of rotational stress is reportedly internal rotation or external rotation . in the present case ,
the dislocation was reduced by internal rotation of the lower leg with knee flexion and reproduced by valgus and external rotation stress .
therefore , valgus and external rotation stress during knee flexion may have been the cause of knee dislocation in our patient .
reportedly , the mcl , acl , and pcl are usually completely ruptured in posterolateral knee dislocation , whereas the posterolateral structures are usually left intact ; however , some recent studies have shown that a posterolateral injury may occur in combination with this type of dislocation .
therefore , combined ligament injuries should be carefully assessed by magnetic resonance imaging ( mri ) or physical examination after reduction . in the present case , complete tearing of the mcl and pcl
however , the acl in our case was only partially torn and exhibited no instability .
only one report by jeevannavar et al . has described a partial acl tear associated with posterolateral knee dislocation .
the remaining acls may prevent complete button holing of the medial femoral condyle through the medial retinaculum and produce reducibility .
samini et al . reported cases of this type of dislocation with medial and lateral meniscal injuries . in the present case ,
the first - line therapeutic approach for posterolateral knee dislocation is conventionally considered immediate reduction by open surgery . however , as we demonstrated in the present case of posterolateral rotary dislocation , it may be possible to reduce this injury by closed manipulation . closed manipulation by valgus stress and internal rotation could be tried as a first - line choice .
combined ligament injuries should be treated in consideration of patient age and activities of daily living . in the present case ,
the partial acl tear did not cause any instability , where the pcl injury was left untreated and a posterior drawer test of grade ii was identified at the final follow - up , although no clinical symptoms originated from this instability .
we experienced the case of posterolateral rotary knee dislocation which was reduced by closed manipulation .
this is the first report of a successful closed reduction for posterolateral knee dislocation . in the present case ,
the dislocation was reduced by internal rotation of the lower leg with knee flexion and reproduced by valgus and external rotation stress .
the mechanism of posterolateral knee dislocation was considered valgus and external rotation stress during knee flexion .
posterolateral rotary knee dislocation is a rare orthopedic injury that is considered to be irreducible by closed reduction because of soft tissue incarceration .
however , with the result of the presented case , the closed manipulation by valgus stress and internal rotation could be tried as a firstline choice .
 introduction : posterolateral rotary knee dislocation is a rare orthopedic injury that is considered to be irreducible by closed reduction because of soft tissue incarceration . here , we present a case of posterolateral rotary knee dislocation , which was reduced by closed manipulation.case report : the patientwas a 33-year - old man who sustained a twisting injury to his right knee that was diagnosed as posterolateral rotary knee dislocation by plain radiographs and the characteristic physical finding known as a dimple sign . under general anesthesia , the knee dislocation was reduced by closed manipulation with internal rotation of the lower leg at knee flexion and reproduced by valgus and external rotation stress . 
 there were was complete tear of posterior cruciate ligament , and partial tear of the anterior cruciate ligament which were not reconstructed . 
 the medial collateral ligament that was detached from the femoral footprint was repaired . 
 one year postoperatively , the range of motion was 0145. there was no knee symptom and no ligament instability.conclusion:this is the first report of a successful closed reduction for posterolateral knee dislocation . 
 the mechanism of dislocation was considered valgus and external rotation stress during knee flexion . 
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