Morphological Variances on the Anterior Surface of the Patella: A Cadaveric Study

Abstract

INTRODUCTION The patella is a sesamoid bone within the tendon of the quadriceps muscle that glides over the distal femur with each movement of the knee joint. The morphological characteristics and variability of the posterior articular surface of the patella has been well documented; however, there is a paucity of information available on the anterior surface of the patella, including any morphological changes that may commonly occur. OBJECTIVE The purpose of this study was to determine the incidence of morphological variances, including vertical grooves or osteophytes, on the anterior surface of patellae in cadavers. For the purposes of this study, an anterior patella groove was defined as a palpable and grossly visual indentation not consistent with the perceived natural curvatures of the anterior surface of the patella; and an anterior patella osteophyte was defined as a palpable and grossly visual bony outgrowth that protruded from the perceived natural curvatures of the anterior surface of the patella (see figure 1). METHODS Data were obtained from the bilateral patellae and femurs of 34 embalmed cadavers. Each patella was harvested and stripped of tendinous fibers and periosteum. Measurements taken from the patellae included: patella weight, length, width, and depth; length and width of the posterior articular surface; and the length, width, and depth of any anterior patella morphology, namely grooves or osteophytes. Additionally, femoral length and circumference were measured from each associated lower extremity. Due to ordinality and data outliers, Spearman's rho values were determined between anatomical measurements, which were calculated separately for each gender. RESULTS The average age of the 19 male and 15 female cadavers was 79.35 years (±9.65) with a range of 54-92 years. Of the harvested patellae (n = 68), 30 samples (44.12%) had an anterior patella groove (n=22; ♂ 17, ♀ 5) or osteophyte (n=8; ♂ 6, ♀ 2). The incidence of anterior groove or osteophyte formation was significantly associated with gender (male 60.5% versus female 23.3%, p=0.002), and the size of the grooves or osteophytes tend to increase with age (see figure 2). The remainder of our statistical calculations therefore were stratified by gender. Among the male patellae, there was a marginally significant association with anterior groove or osteophyte formation with increased age (p=0.082 via Mann-Whitney U test). For males, age and patella width were significantly associated with width of the osteophyte (Rs=0.727, -0.881; p=0.041, 0.004, respectively). Among the female patellae, there was a significant association with anterior grooves or osteophytes and decreased patella length (p=0.039 Mann-Whitney U test). CONCLUSIONS The overall incidence of groove or osteophyte formation on the anterior surface of the patella appears to be relatively common in elderly subjects with a rate of 44.12%; with males having a relative risk of 2.594 times higher than females (95% CI 1.291, 5.211). IMPLICATIONS Whether the presence of grooves or osteophytes on the anterior surface of the patella are a normal consequence of aging and quadriceps usage, or are indicative of pathologies, such as patella tendinitis with accompanying clinical findings, remains to be explored.