title: Traumatic Patellar Dislocation and Cartilage Injury: A Follow-up Study of Long-Term Cartilage Deterioration.
abstract: BACKGROUND
  Patellofemoral cartilage deterioration and osteoarthritis are reported to be associated with recurrent patellar dislocation. However, the association between first-time traumatic patellar dislocation and cartilage deterioration is unknown.
  
  
  OBJECTIVE
  The aim of this study was to assess long-term cartilage deterioration in the patellofemoral and tibiofemoral joint after conservatively treated traumatic lateral patellar dislocation.
  
  
  METHODS
  Case series; Level of evidence, 4.
  
  
  METHODS
  Twenty patients (mean age, 25 years) who sustained first-time traumatic lateral patellar dislocation with no previous patellofemoral instability symptoms were initially scanned with 1.5-T magnetic resonance imaging (MRI). A follow-up 3-T MRI was conducted, on average, 8 years after first-time lateral patellar dislocation. Subjective instability symptoms and Knee injury and Osteoarthritis Outcome Score were also assessed.
  
  
  RESULTS
  In the primary MRI, patellofemoral cartilage injury was seen in 14 of 20 patients (70%). Most (14/15) of the injuries were seen in the patellar cartilage, especially at the medial facet. On the follow-up MRI, patellofemoral cartilage deterioration was visible for all patients. The central patella ( P = .005) seemed especially prone to cartilage deterioration during the follow-up. Half of the patients (10/20) had grade 3-4 cartilage lesions in the patellofemoral joint in the follow-up MRI. In the primary MRI, only 1 patient exhibited tibiofemoral joint cartilage lesions, whereas at the time of follow-up, 10 of 20 patients exhibited tibiofemoral cartilage lesions. The majority of these lesions were considered clinically nonsignificant (International Cartilage Repair Society = 1) and were seen in the lateral compartment (6/10, 60%). Of the 14 patients (36%) with injury to the patellar cartilage, 5 reported subsequent instability of the patellofemoral joint, but this was not associated with more significant cartilage deterioration in the follow-up MRI compared with patients without redislocation.
  
  
  CONCLUSIONS
  While recurrent lateral patellar dislocation is known to lead to degenerative process, a single first-time or infrequently recurring traumatic lateral patellar dislocation also seems to be associated with gradual cartilage deterioration. Traumatic lateral patellar dislocation might initiate gradual degeneration of the cartilage in the patellofemoral joint and can lead to the development of generalized knee osteoarthritis. Instability symptoms of the patellofemoral joint, however, were not related to the severity of the deterioration.
authors.affiliation: Department of Orthopedics, Unit of Musculoskeletal Surgery, Tampere University Hospital, Tampere, Finland.
authors.forename: Essi E
authors.initials: EE
authors.lastname: Salonen
authors.affiliation: Medical Imaging Centre, Tampere University Hospital, Tampere, Finland.
authors.forename: Teemu
authors.initials: T
authors.lastname: Magga
authors.affiliation: Dextra Hospital, Tampere, Finland.
authors.forename: Petri J
authors.initials: PJ
authors.lastname: Sillanpää
authors.affiliation: Medical Imaging Centre, Tampere University Hospital, Tampere, Finland.
authors.forename: Tommi
authors.initials: T
authors.lastname: Kiekara
authors.affiliation: Department of Orthopedics, Unit of Musculoskeletal Surgery, Tampere University Hospital, Tampere, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Mäenpää
authors.affiliation: Department of Orthopedics, Unit of Musculoskeletal Surgery, Tampere University Hospital, Tampere, Finland.
authors.forename: Ville M
authors.initials: VM
authors.lastname: Mattila
mesh_terms: D000328:Adult; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000293:injuries* / Q000473:pathology*; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology; D031222:Patellar Dislocation / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D057071:Patellofemoral Joint / Q000000981:diagnostic imaging / Q000293:injuries / Q000473:pathology; D012008:Recurrence; D055815:Young Adult
keywords: cartilage deterioration; knee osteoarthritis; lateral patellar dislocation; patellofemoral instability; patellofemoral osteoarthritis