Position of the Patella among Emirati Adult Knees. Is Insall-Salvati Ratio Applicable to Middle-Easterners?

Document Type : RESEARCH PAPER


1 Department of Surgery, United Arab Emirates University, Al Ain, UAE

2 Rothman Institute at Thomas Jefferson University, Philadelphia, PA, USA


Background: Abnormal patellar height is associated with anterior knee pain and several conditions that affect the patellofemoral joint. The aim of this study was to 1) report the incidence of patella alta and patella baja and 2) investigate whether the normal limits of the Insall-Salvati ratio is applicable in adult Middle-Easterners.
Methods: A radiographic review of the lateral radiographs of 736 Middle-Eastern knees were performed. Patellar tendon length (TL) and the patellar length (TP) was digitally measured and the ratios of these measures was used to calculate the Insall-Salvati ratio.
Results: The overall mean TL/PL ratio was 1.20±0.17. The Insall-Salvati ratio was higher (p=0.0013) in males (1.22± 0.12) than in females (1.18±0.17). According to our measurement, the recommended levels for defining abnormal patellar position should be 0.86 for patella baja and 1.54 for patella alta.
Conclusion: The use of TL/PL ratio demonstrated a higher incidence of patella alta and a higher mean TL/PL ratio compared to other techniques. The normal ranges for the TL/PL differs from western populations and may be attributed to lifestyle differences.


  1. Hauser ED. Total tendon transplant for slipping patella: a new operation for recurrent dislocation of the patella. 1938. Clin Orthop Relat Res. 2006; 452(5):7-16.
  2. Lewallen LW, McIntosh AL, Dahm DL. Predictors of recurrent instability after acute patellofemoral dislocation in pediatric and adolescent patients. Am J Sports Med. 2013; 41(3):575-81.
  3. Rogers BA. Patella alta: association with patellofemoral alignment and changes in contact area during weight-bearing. J Bone Joint Surg Am. 2008; 90(2):446-7.
  4. Kujala UM, Osterman K, Kvist M, Aalto T, Friberg O. Factors predisposing to patellar chondropathy and patellar apicitis in athletes. Int Orthop. 1986; 10(3):195-200.
  5. Stefanik JJ, Zhu Y, Zumwalt AC, Gross KD, Clancy M, Lynch JA, et al. Association between patella alta and the prevalence and worsening of structural features of patellofemoral joint osteoarthritis: the multicenter osteoarthritis study. Arthritis Care Res. 2010; 62(9):1258-65.
  6. Jakob RP, von Gumppenberg S, Engelhardt P. Does Osgood--Schlatter disease influence the position of the patella? J Bone Joint Surg Br. 1981; 63B(4):579-82.
  7. Aparicio G, Abril JC, Calvo E, Alvarez L. Radiologic study of patellar height in Osgood-Schlatter disease. J Pediatr Orthop. 1997; 17(1):63-6.
  8. Noyes FR, Mayfield W, Barber-Westin SD, Albright JC, Heckmann TP. Opening wedge high tibial osteotomy: an operative technique and rehabilitation program to decrease complications and promote early union and function. Am J Sports Med. 2006; 34(8):1262-73.
  9. Noyes FR, Wojtys EM, Marshall MT. The early diagnosis and treatment of developmental patella infera syndrome. Clin Orthop Relat Res. 1991; 265(7):241-52.
  10. Mahfouz M, Abdel Fatah EE, Bowers LS, Scuderi G. Three-dimensional morphology of the knee reveals ethnic differences. Clin Orthop Relat Res. 2012; 470(1):172-85.
  11. Insall J, Salvati E. Patella position in the normal knee joint. Radiology. 1971; 101(1):101-4.
  12. Shabshin N, Schweitzer ME, Morrison WB, Parker L. MRI criteria for patella alta and baja. Skeletal Radiol. 2004; 33(8):445-50.
  13. Hamed AD. Radiological assessment of the patella position in the normal knee of adult Nigerians. East Afr Med J. 1990; 67(6):442-6.
  14. Ahmed AD. Radiological assessment of the patella position in the normal knee joint of adult Nigerians. West Afr J Med. 1992; 11(1):29-33.
  15. Upadhyay S, Raza HK, Srivastava P. Position of the patella in adults in central India: evaluation of the Insall-Salvati ratio. J Orthop Surg. 2013; 21(1):23-7.
  16. Leung YF, Wai YL, Leung YC. Patella alta in southern China. A new method of measurement. Int Orthop. 1996; 20(5):305-10.
  17. Grelsamer RP, Meadows S. The modified Insall-Salvati ratio for assessment of patellar height. Clin Orthop Relat Res. 1992; 282(2):170-6.
  18. Phillips CL, Silver DA, Schranz PJ, Mandalia V. The measurement of patellar height: a review of the methods of imaging. J Bone Joint Surg Br. 2010; 92(8):1045-53.
  19. Blackburne JS, Peel TE. A new method of measuring patellar height. J Bone Joint Surg Br. 1977; 59(2):241-2.
  20. Dorfl J. Migration of tendinous insertions. I. Cause and mechanism. J Anat. 1980; 131(Pt 1):179-95.