Patella Height in Different Ethnic Populations: An Observational Multicenter Study.

Patella height appears to have a crucial role in knee biomechanics. Patellar malalignment and maltracking are therefore believed to be associated with development and progression of patellofemoral pain and disease. Published data are scant regarding the effect of everyday tasks on patella height and patellofemoral disease. We included 150 subjects in a retrospective observational study. Group A had 75 subjects (24 male and 51 female, with a mean age of 58.5 yr), whose daily activities included squatting (the traditional Muslim praying position called Sujud). Group B had 75 subjects (42 male and 33 female, with a mean age of 47.6 yr), who were non-Muslim. Patella height was measured using Insall-Salvati (IS) and Blackburne-Peel (BP) ratios. The mean IS ratio was 0.86 (confidence interval [CI]: 0.7-1.02) for group A and 1.1 (CI: 0.96-1.23) for group B. The mean BP ratio was 0.66 (CI: 0.49-0.83) for group A and 0.89 (CI: 0.73-1.04) for group B. We found 26 subjects (34.7%) in group B to have patella alta, when measured by either ratio, compared to one subject (1.3%) in group A (p < 0.01) with patella alta. We found 61 subjects (81.3%) in group A to have patella baja, when measured by either ratio, compared to 21 subjects (28%) in group A (p < 0.01) with patella baja. In group A, the IS ratio was reduced in 29 subjects (38.7%), the BP ratio was reduced in 59 subjects (78.7%), and both were reduced in 27 subjects (36%). A similar pattern was noted for group B. Our results show that a significant increase in patella baja was associated with repeated squatting/kneeling, compared to the predominance of patella alta in the control group. On the basis of these findings, we hypothesize that biomechanical stresses associated with repeated hyperflexion of the knee asymmetrically affect the more flexible quadriceps muscle fibers greater than patella tendon fibers. Thus, repeated hyperflexion in everyday tasks leads to elongation of quadriceps fibers and patella baja.