Is There an Association Between Superolateral Hoffa Fat Pad Edema on MRI and Clinical Evidence of Fat Pad Impingement?

Department of Radiology, University of Wisconsin School of Medicine and Public Health, 600 Highland Ave, Madison WI 53792.
American Journal of Roentgenology (Impact Factor: 2.73). 11/2012; 199(5):1099-104. DOI: 10.2214/AJR.12.8798
Source: PubMed


Patients with symptomatic Hoffa fat pad impingement often exhibit fat pad edema on MRI. We studied two patient groups to determine the association between MRI fat pad edema and clinical symptoms of Hoffa fat pad impingement.
We studied 34 consecutive patients with an MRI diagnosis of fat pad edema and no injury in the prior year (group 1) and 47 consecutive patients with a knee MRI examination and no injury in the prior year (group 2). Two sports medicine physicians reviewed the clinical records to confirm or exclude symptomatic fat pad impingement. Two musculoskeletal radiologists independently scored 12 Hoffa fat pad locations for the presence of edema, noting the epicenter.
Seventeen of the 34 patients in group 1 had clinical symptoms of fat pad impingement, with all 34 having fat pad edema. There was no association between clinical fat pad impingement and fat pad edema in any specific location (p > 0.183), but patients with fat pad impingement had a greater number of regions of edema (p = 0.005, 0.026 for two observers). In group 2, all four patients with clinical fat pad impingement had MRI fat pad edema, but 38 of the 43 patients without clinical impingement had MRI fat edema; 11 of the 38 had edema centered in the superolateral fat pad.
Edema is present on MRI in the superolateral region of Hoffa fat pad in patients with clinical fat pad impingement. However, such edema can also be present in patients without symptoms of fat pad impingement.

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    • "Moreover a high-riding patella, a short distance between the patellar ligament and the lateral trochlear facet, and an increased distance from the tibial tubercle to the trochlear groove are associated with superolateral Hoffa's fat pad edema at MR imaging [8]. Nevertheless patients with symptomatic IPF impingement often exhibit fat pad edema on MRI in the superolateral region of Hoffa's fat pad [9]. Finally edema in the superolateral portion of IFP is usually associated with patellar maltracking [10]. "
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    ABSTRACT: Background Liposynovitis prepatellaris (Hoffa’s syndrome) is a rare condition in children and rarely discussed in the literature. Hoffa’s syndrome can lead to an obscure anterior knee pain resulting from impingement and inflammation of the infrapatellar fat pad.Aim of the workThe aim of this case report is to increase awareness among rheumatologists about this condition among children to avoid erroneous diagnosis of juvenile idiopathic arthritis (JIA) and unnecessary treatment with disease-modifying antirheumatic drugs (DMARDs).Case reportIn this report we presented a 12 year-old child with this condition who presented with chronic pain and intermittent swelling involving his right knee. The patient was wrongly diagnosed as a case of JIA and wrongly treated with DMARDs for three years duration. The report will shed light on the characteristic MRI features of this condition and the value to order MRI in such atypical presentation.Conclusion Hoffa’s syndrome can present with chronic arthropathy in children that can mimic mono-articular JIA presentation and eventually unnecessary treatment with DMARDs. MRI is generally very helpful from the diagnostic point of view, it clearly depicts Hoffa’s infrapatellar fat pad entrapment and its findings may suggest Hoffa’s syndrome.
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    ABSTRACT: Objective: Superolateral Hoffa fat-pad edema is a frequent finding with patellar maltracking and may precede clinically significant chondrosis. The purpose of this study was to clarify which patellofemoral measurements are most highly associated and to develop a prediction rule to guide clinical decision making. Materials and methods: Twenty-three patellofemoral measurements were performed on 71 knees retrospectively identified as having superolateral Hoffa fat-pad edema at MRI (Hoffa group) and on 45 normal knees (normal group). Univariate analysis was performed to examine the association between these measurements and Hoffa fat-pad edema. Classification and regression tree analysis with 10-fold cross validation was used to generate a prediction model. Results: For 16 of the 23 patellofemoral measurements, there was a statistically significant difference (p < 0.05) between the Hoffa and normal groups. Classification and regression tree analysis identified a prediction model in which a patient is placed into the Hoffa group if one of three conditions is met: lateral patellar displacement greater than -3.6 mm and Insall-Salvati ratio greater than 0.99; lateral patellar displacement of -3.6 mm or less and Insall-Salvati ratio greater than 1.23; or lateral patellar displacement of -3.6 mm or less, Insall-Salvati ratio of 1.23 or less, and lateral trochlear inclination of 16.5° or less. In fitting of the original sample, this model had 91.6% sensitivity and 88.9% specificity for identifying the Hoffa group. When 10-fold cross validation was applied, the estimated generalizable sensitivity and specificity were 85.9% and 75.6%. Conclusion: Superolateral Hoffa fat-pad is strongly associated with a number of measures of patellar maltracking. A prediction model based on these measurements is accurate for differentiating knees with superolateral Hoffa fat-pad edema from normal knees.
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