Lateral dislocation of patella out of femoral trochlear groove due to twisting/pivoting injury of knee
Usually transient: spontaneous relocation typical
Pertinent anatomy: medial patellofemoral ligament (MPFL) = sheet of collagen attaching to superior 1/2 of patella, MFC just above origin of medial collateral ligament
Primary soft tissue restraint against lateral patella dislocation
Medial retinaculum attaches to lower 1/2 of patella
Trochlear sulcus angle: angle between medial and lateral facets, measured at deepest point ~ 2 cm above joint
Usually easy to "eyeball" measurement as normal or abnormal
IMAGING
General Features
Radiographic Findings
CT Findings
MR Findings
Ultrasonographic Findings
Imaging Recommendations
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Staging, Grading, & Classification
CLINICAL ISSUES
Presentation
Demographics
Natural History & Prognosis
Treatment
DIAGNOSTIC CHECKLIST
Consider
Image Interpretation Pearls
Reporting Tips
Selected References
Aicale R et al: Combined medial patellofemoral and medial patellotibial reconstruction for patellar instability: a PRISMA systematic review. J Orthop Surg Res. 15(1):529, 2020
Grimm NL et al: Traumatic patellar dislocations in childhood and adolescents. Orthop Clin North Am. 51(4):481-91, 2020
Jiang B et al: Evaluation of risk correlation between recurrence of patellar dislocation and damage to the medial patellofemoral ligament in different sites caused by primary patellar dislocation by MRI: a meta-analysis. J Orthop Surg Res. 15(1):461, 2020
McMahon CJ et al: The extensor mechanism: imaging and intervention. Semin Musculoskelet Radiol. 21(2):89-101, 2017
de Oliveira V et al: Medial patellofemoral ligament anatomy: is it a predisposing factor for lateral patellar dislocation? Int Orthop. 38(8):1633-9, 2014
Reagan J et al: MPFL reconstruction: technique and results. Clin Sports Med. 33(3):501-16, 2014
Sillanpää PJ et al: Medial patellofemoral ligament avulsion injury at the patella: classification and clinical outcome. Knee Surg Sports Traumatol Arthrosc. 22(10):2414-8, 2014
Torabi M et al: MRI evaluation and complications of medial patellofemoral ligament reconstruction. Clin Imaging. 39(1):116-27, 2014
Zhang GY et al: Evaluation of medial patellofemoral ligament tears after acute lateral patellar dislocation: comparison of high-frequency ultrasound and MR. Eur Radiol. 25(1):274-81, 2014
Earhart C et al: Transient lateral patellar dislocation: review of imaging findings, patellofemoral anatomy, and treatment options. Emerg Radiol. 20(1):11-23, 2013
Camanho GL et al: Conservative versus surgical treatment for repair of the medial patellofemoral ligament in acute dislocations of the patella. Arthroscopy. 25(6):620-5, 2009
Kapur S et al: Acute knee dislocation: review of an elusive entity. Curr Probl Diagn Radiol. 38(6):237-50, 2009
Kitamura K et al: Avulsion-tear type medial patellofemoral ligament injury with a small bony fragment in lateral patellar dislocation. J Trauma. 66(1):271-3, 2009
Le Corroller T et al: Transient medial patellar dislocation: injury patterns at US and MR imaging. Skeletal Radiol. 38(5):519-23, 2009
Nietosvaara Y et al: Acute patellar dislocation in children and adolescents. Surgical technique. J Bone Joint Surg Am. 91 Suppl 2 Pt 1:139-45, 2009
Andrish J: The management of recurrent patellar dislocation. Orthop Clin North Am. 39(3):313-27, vi, 2008
Christiansen SE et al: Isolated repair of the medial patellofemoral ligament in primary dislocation of the patella: a prospective randomized study. Arthroscopy. 24(8):881-7, 2008
Colvin AC et al: Patellar instability. J Bone Joint Surg Am. 90(12):2751-62, 2008
Panagopoulos A et al: MPFL reconstruction for recurrent patella dislocation: a new surgical technique and review of the literature. Int J Sports Med. 29(5):359-65, 2008
Robinson RJ et al: Wii knee. Emerg Radiol. 15(4):255-7, 2008
Feibel RJ et al: Irreducible lateral patellar dislocation: the importance of impaction fracture recognition. J Emerg Med. 33(1):11-5, 2007
Sanders TG et al: MRI of osteochondral defects of the lateral femoral condyle: incidence and pattern of injury after transient lateral dislocation of the patella. AJR Am J Roentgenol. 187(5):1332-7, 2006
Elias DA et al: Imaging of patellofemoral disorders. Clin Radiol. 59(7):543-57, 2004
O'Reilly MA et al: Sonographic appearances of medial retinacular complex injury in transient patellar dislocation. Clin Radiol. 58(8):636-41, 2003
Sanders TG et al: Medial patellofemoral ligament injury following acute transient dislocation of the patella: MR findings with surgical correlation in 14 patients. J Comput Assist Tomogr. 25(6):957-62, 2001
Sonin AH et al: MR imaging appearance of the extensor mechanism of the knee: functional anatomy and injury patterns. Radiographics. 15(2):367-82, 1995
Kirsch MD et al: Transient lateral patellar dislocation: diagnosis with MR imaging. AJR Am J Roentgenol. 161(1):109-13, 1993
Lateral dislocation of patella out of femoral trochlear groove due to twisting/pivoting injury of knee
Usually transient: spontaneous relocation typical
Pertinent anatomy: medial patellofemoral ligament (MPFL) = sheet of collagen attaching to superior 1/2 of patella, MFC just above origin of medial collateral ligament
Primary soft tissue restraint against lateral patella dislocation
Medial retinaculum attaches to lower 1/2 of patella
Trochlear sulcus angle: angle between medial and lateral facets, measured at deepest point ~ 2 cm above joint
Usually easy to "eyeball" measurement as normal or abnormal
IMAGING
General Features
Radiographic Findings
CT Findings
MR Findings
Ultrasonographic Findings
Imaging Recommendations
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Staging, Grading, & Classification
CLINICAL ISSUES
Presentation
Demographics
Natural History & Prognosis
Treatment
DIAGNOSTIC CHECKLIST
Consider
Image Interpretation Pearls
Reporting Tips
Selected References
Aicale R et al: Combined medial patellofemoral and medial patellotibial reconstruction for patellar instability: a PRISMA systematic review. J Orthop Surg Res. 15(1):529, 2020
Grimm NL et al: Traumatic patellar dislocations in childhood and adolescents. Orthop Clin North Am. 51(4):481-91, 2020
Jiang B et al: Evaluation of risk correlation between recurrence of patellar dislocation and damage to the medial patellofemoral ligament in different sites caused by primary patellar dislocation by MRI: a meta-analysis. J Orthop Surg Res. 15(1):461, 2020
McMahon CJ et al: The extensor mechanism: imaging and intervention. Semin Musculoskelet Radiol. 21(2):89-101, 2017
de Oliveira V et al: Medial patellofemoral ligament anatomy: is it a predisposing factor for lateral patellar dislocation? Int Orthop. 38(8):1633-9, 2014
Reagan J et al: MPFL reconstruction: technique and results. Clin Sports Med. 33(3):501-16, 2014
Sillanpää PJ et al: Medial patellofemoral ligament avulsion injury at the patella: classification and clinical outcome. Knee Surg Sports Traumatol Arthrosc. 22(10):2414-8, 2014
Torabi M et al: MRI evaluation and complications of medial patellofemoral ligament reconstruction. Clin Imaging. 39(1):116-27, 2014
Zhang GY et al: Evaluation of medial patellofemoral ligament tears after acute lateral patellar dislocation: comparison of high-frequency ultrasound and MR. Eur Radiol. 25(1):274-81, 2014
Earhart C et al: Transient lateral patellar dislocation: review of imaging findings, patellofemoral anatomy, and treatment options. Emerg Radiol. 20(1):11-23, 2013
Camanho GL et al: Conservative versus surgical treatment for repair of the medial patellofemoral ligament in acute dislocations of the patella. Arthroscopy. 25(6):620-5, 2009
Kapur S et al: Acute knee dislocation: review of an elusive entity. Curr Probl Diagn Radiol. 38(6):237-50, 2009
Kitamura K et al: Avulsion-tear type medial patellofemoral ligament injury with a small bony fragment in lateral patellar dislocation. J Trauma. 66(1):271-3, 2009
Le Corroller T et al: Transient medial patellar dislocation: injury patterns at US and MR imaging. Skeletal Radiol. 38(5):519-23, 2009
Nietosvaara Y et al: Acute patellar dislocation in children and adolescents. Surgical technique. J Bone Joint Surg Am. 91 Suppl 2 Pt 1:139-45, 2009
Andrish J: The management of recurrent patellar dislocation. Orthop Clin North Am. 39(3):313-27, vi, 2008
Christiansen SE et al: Isolated repair of the medial patellofemoral ligament in primary dislocation of the patella: a prospective randomized study. Arthroscopy. 24(8):881-7, 2008
Colvin AC et al: Patellar instability. J Bone Joint Surg Am. 90(12):2751-62, 2008
Panagopoulos A et al: MPFL reconstruction for recurrent patella dislocation: a new surgical technique and review of the literature. Int J Sports Med. 29(5):359-65, 2008
Robinson RJ et al: Wii knee. Emerg Radiol. 15(4):255-7, 2008
Feibel RJ et al: Irreducible lateral patellar dislocation: the importance of impaction fracture recognition. J Emerg Med. 33(1):11-5, 2007
Sanders TG et al: MRI of osteochondral defects of the lateral femoral condyle: incidence and pattern of injury after transient lateral dislocation of the patella. AJR Am J Roentgenol. 187(5):1332-7, 2006
Elias DA et al: Imaging of patellofemoral disorders. Clin Radiol. 59(7):543-57, 2004
O'Reilly MA et al: Sonographic appearances of medial retinacular complex injury in transient patellar dislocation. Clin Radiol. 58(8):636-41, 2003
Sanders TG et al: Medial patellofemoral ligament injury following acute transient dislocation of the patella: MR findings with surgical correlation in 14 patients. J Comput Assist Tomogr. 25(6):957-62, 2001
Sonin AH et al: MR imaging appearance of the extensor mechanism of the knee: functional anatomy and injury patterns. Radiographics. 15(2):367-82, 1995
Kirsch MD et al: Transient lateral patellar dislocation: diagnosis with MR imaging. AJR Am J Roentgenol. 161(1):109-13, 1993
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