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KEY FACTS
Terminology
Imaging
Top Differential Diagnoses
Pathology
Clinical Issues
Diagnostic Checklist
TERMINOLOGY
Abbreviations
- Transient patella dislocation (TPD), lateral femoral condyle (LFC), medial femoral condyle (MFC), vastus medialis obliquus (VMO)
Synonyms
- Transient patellar dislocation, patella dislocation, patella subluxation, transient dislocation of patella
Definitions
- 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
- Trochlear dysplasia = abnormally flat sulcus angle, > 145°
- 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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References
Tables
Tables
KEY FACTS
Terminology
Imaging
Top Differential Diagnoses
Pathology
Clinical Issues
Diagnostic Checklist
TERMINOLOGY
Abbreviations
- Transient patella dislocation (TPD), lateral femoral condyle (LFC), medial femoral condyle (MFC), vastus medialis obliquus (VMO)
Synonyms
- Transient patellar dislocation, patella dislocation, patella subluxation, transient dislocation of patella
Definitions
- 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
- Trochlear dysplasia = abnormally flat sulcus angle, > 145°
- 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
