Association between patellofemoral joint alignment and morphology to superlateral Hoffa's fat pad edema
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BACKGROUND: Osteoarthritis is a leading cause of disability in people of 65 and older. Researches have shown several possible factors leading to knee osteoarthritis development. Patellofemoral joint maltracking has been thought to be associated with or caused edema in the knee; which is thought to be the early signs of osteoarthritis. Hoffa's fat pad is an intra-articular component of knee located under the kneecap. It has also been suggested as one marker for osteoarthritis, when MRI shows a presence of edema in it. Recently, edema in the superolateral region of Hoffa's fat pad has been hypothesized as a distinct signal than the edema on other regions. There is an interest in finding the relation of this superolateral edema with other factors of osteoarthritis development. OBJECTIVE: This thesis research project is aimed to assess the relation of kneecap-thighbone (patellofemoral) joint alignment, femoral trochlea morphology, and patellar height to edema in the superolateral region of Hoffa’s fat pad especially in the population with average age above 65 years old. The hypothesis is that the flatter trochlear morphology and abnormal patella alignment will have higher risk of superolateral edema. METHODS: This is a cross-sectional study using a subset data from Multicenter Osteoarthritis (MOST) study, specifically at 60-month visit. This study measured the patellofemoral measurements (sulcus angle, lateral and medial trochlear inclination angle, trochlear angle, Insall-Salvati ratio, patellar tilt angle, and bisect offset) as the predictor variables, and semiquantitative scoring of MRI edema in superolateral Hoffa’s fat pad as the outcome variable. Logistic regression analyses were performed to find the strongly associated patellofemoral measurements to superolateral Hoffa’s fat pad edema. RESULTS: From the logistic regression analysis, trochlear angle, Insall-Salvati ratio, and bisect offset were highly associated with the superolateral edema. A further analysis, by categorizing the measurements to quartiles, was found that only the highest quartiles of both bisect offset and trochlear angle are associated with superolateral Hoffa’s fat pad edema when compared to the reference quartile. All quartiles of Insall-Salvati ratio are strongly associated with superolateral edema when compared to the reference quartile. CONCLUSION: Current study presents that people above 65 years old with high trochlear angle, extreme lateral patellar translation or bisect offset, and high patella riding have high risk of having superolateral Hoffa’s fat pad edema.