title: Sagittal plane tilting deformity of the patellofemoral joint: a new concept in patients with chondromalacia patella.
abstract: OBJECTIVE
  The aims of this study were to evaluate sagittal plane alignment in patients with chondromalacia patella via magnetic resonance imaging (MRI), analyse the relationships between the location of the patellar cartilaginous lesions and sagittal alignment and finally investigate the relationships between the sagittal plane malalignment and patellofemoral loadings using by finite element analysis.
  
  
  METHODS
  Fifty-one patients who were diagnosed with isolated modified Outerbridge grade 3-4 patellar chondromalacia based on MRI evaluation and 51 control subjects were evaluated. Chondromalacia patella patients were divided into three subgroups according to the chondral lesion location as superior, middle and inferior. The patella-patellar tendon angle (P-PT) was used for evaluation of sagittal alignment of patellofemoral joint. Each subgroup was compared with control group by using P-PT angle. To investigate the biomechanical effects of sagittal plane malpositioning on patellofemoral joint, bone models were created at 30°, 60° and 90° knee flexion by using mean P-PT angles, which obtained from patients with chondromalacia patellae and control subjects. The total loading and contact area values of the patellofemoral joints were investigated by finite element analysis.
  
  
  RESULTS
  The mean age of all participants was 52.9 ± 8.2 years. The mean P-PT angle was significantly lower in chondromalacia group (142.1° ± 3.6°) compared to control group (144.5° ± 5.3°) (p = 0.008). Chondral lesions were located in superior, middle and inferior zones in 16, 20 and 15 patients, respectively. The mean P-PT angles in patients with superior (141.8 ± 2.7) and inferior subgroups (139.2 ± 2.3) were significantly lower than the values in the control group (p < 0.05). The contact area values were detected higher in models with chondromalacia than in the control models at the same flexion degrees. There were increased loadings at 30° and 90° flexions in the sagittal patellar tilt models.
  
  
  CONCLUSIONS
  This study revealed that sagittal plain malpositioning of the patellofemoral joint might be related to chondromalacia, especially in the presence of lesions in the upper and lower part of the patella. This condition leads to supraphysiological loadings on the patellofemoral joint. Sagittal patellar tilt should be considered in the evaluation and management of patellar cartilage defects. Taking sagittal plane malalignment into consideration in patellofemoral joint evaluation will enable us to design new physical and surgical modalities.
  
  
  METHODS
  IV.
authors.affiliation: Department of Orthopedics and Traumatology, Medical Park Hospital, Ankara, Turkey. ertugrul_aksahin@hotmail.com.
authors.forename: Ertugrul
authors.initials: E
authors.lastname: Aksahin
authors.affiliation: Department of Orthopedics and Traumatology, Faculty of Medicine, Yıldırım Beyazıt University, Ankara, Turkey.
authors.forename: Cem Nuri
authors.initials: CN
authors.lastname: Aktekin
authors.affiliation: Orthopedics and Traumatology Department, Ankara Education and Research Hospital, Ankara, Turkey.
authors.forename: Onur
authors.initials: O
authors.lastname: Kocadal
authors.affiliation: Radiology Department, Ankara Numune Education and Research Hospital, Ankara, Turkey.
authors.forename: Semra
authors.initials: S
authors.lastname: Duran
authors.affiliation: Department of Orthopedics and Traumatology, Faculty of Medicine, Eskisehir Osmangazi University, Eskisehir, Turkey.
authors.forename: Cüneyd
authors.initials: C
authors.lastname: Gunay
authors.affiliation: Department of Physical Therapy and Rehabilitation, Faculty of Health Science, University of Uskudar, Istanbul, Turkey.
authors.forename: Defne
authors.initials: D
authors.lastname: Kaya
authors.affiliation: Department of Orthopedics and Traumatology, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey.
authors.forename: Onur
authors.initials: O
authors.lastname: Hapa
authors.affiliation: Orthopedics and Traumatology Department, Ankara Education and Research Hospital, Ankara, Turkey.
authors.forename: Murad
authors.initials: M
authors.lastname: Pepe
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D046789:Chondromalacia Patellae / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D057071:Patellofemoral Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D016059:Range of Motion, Articular / Q000502:physiology; D012189:Retrospective Studies; D016474:Weight-Bearing
keywords: Chondromalacia patella; Finite element analysis; Patellofemoral; Sagittal tilt