Korean J Radiol.  2018 Apr;19(2):292-300. 10.3348/kjr.2018.19.2.292.

The Correlation between the Injury Patterns of the Medial Patellofemoral Ligament in an Acute First-Time Lateral Patellar Dislocation on MR Imaging and the Incidence of a Second-Time Lateral Patellar Dislocation

  • 1Department of Ultrasonography, Shandong Provincial Qianfoshan Hospital of Shandong University, Jinan 250014, China. qydinghy@163.com
  • 2Department of Ultrasonography, The Second People's Hospital of Liaocheng, Liaocheng 252601, China.
  • 3Department of Ultrasonography, Jinan Third People's Hospital, Jinan 250132, China.
  • 4Department of Radiology, Shandong Provincial Qianfoshan Hospital of Shandong University, Jinan 250014, China.
  • 5Department of Radiology, Shandong Provincial Corps Hospital of Chinese People's Armed Police Force, Jinan 250014, China.
  • 6Department of Orthopedics, Shandong Provincial Qianfoshan Hospital of Shandong University, Jinan 250014, China.


To evaluate the correlation between the injury patterns of the medial patellofemoral ligament (MPFL) on magnetic resonance imaging in an acute first-time lateral patellar dislocation (LPD) and incidence of a second-time LPD.
Magnetic resonance images were prospectively analyzed in 147 patients after an acute first-time LPD with identical nonoperative management. The injury patterns of MPFL in acute first-time LPDs were grouped by location and severity for the analysis of the incidence of second-time LPD in a 5-year follow-up. Independent t tests, chi-square tests and Kruskal-Wallis tests were performed as appropriate.
Forty-six cases (46/147, 31.3%) of second-time LPD were present at the 5-year follow-up. Fourteen (14/62, 22.6%) and 31 cases (31/80, 38.8%) were present in the partial and complete MPFL tear subgroups, respectively. Twenty-five cases (25/65, 38.5%), 11 cases (11/26, 42.3%), and 8 cases (8/47, 17%) were present in the isolated femoral-side MPFL tear (FEM), combined MPFL tear (COM), and isolated patellar-side MPFL tear (PAT) subgroups, respectively. Compared with the partial MPFL tears, complete tears showed higher incidence of a second-time LPD (p = 0.04). The time interval between the two LPDs was shorter in the complete MPFL tear subgroup (24.2 months) than in the partial tear subgroup (36.9 months, p = 0.001). Compared with the PAT subgroup, the FEM and COM subgroups showed a higher incidence of a second-time LPD (p = 0.025). The time intervals between the two LPDs were shorter in the FEM and COM subgroups (20.8 months and 19.2 months) than in the PAT subgroup (32.5 months, p = 0.049).
A complete MPFL tear, isolated femoral-side tear and combined tear in a first-time LPD predispose a second-time LPD.


Patellar dislocation; Knee; Medial patellofemoral ligament; Recurrence; MRI

MeSH Terms

Follow-Up Studies
Magnetic Resonance Imaging*
Patellar Dislocation*
Prospective Studies
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