Comparisons of patellar bone mineral density between individuals with and without patellofemoral pain.

BACKGROUND: Although bone stress injuries have been reported in individuals with patellofemoral pain (PFP), especially within the lateral patella, it remains unclear whether persons with PFP exhibit altered patellar regional bone mineral density (BMD). The primary purpose of this study was to compare BMD of the patella (lateral, medial, and total regions) between individuals with and without PFP using quantitative computed tomography (QCT). The secondary aim was to examine the associations between patellar regional BMD and patellofemoral joint (PFJ) alignment. METHODS: Ten individuals with retropatellar pain and 10 sex, age, weight, height, and activity matched pain-free controls underwent a QCT scan to obtain patellar BMD. To quantify PFJ alignment, patellar lateral displacement was measured using bisect-offset (BSO) index and patellar mediolateral tilt was quantified using patellar tilt angle (PTA). A two-factor repeated-measures ANOVA was used to compare BMD across the three patellar regions and between the two groups. Pearson correlation coefficient analyses were used to evaluate the associations between BMD and PFJ alignment of all participants. RESULTS: There was no difference in BMD between the two groups. However, BMD was highest within the lateral patella and was lowest within the medial patella across both groups. There were significantly moderate to large correlations between BSO index/PTA and BMD within lateral, medial, and total regions. CONCLUSIONS: While individuals with PFP and pain-free controls have similar patellar BMD, the lateral patella exhibits the highest BMD. Additionally, higher patellar regional BMD is related to increased patellar lateral displacement and lateral tilt.