IntroductionLarge ganglionic cystic formations arising from the infrapatellar fat pad are quite uncommon and only a few are mentioned in the literature. An open excision in these cases is mandatory.Case presentationWe report the case of a large infrapatellar fat pad ganglion in a 37-year-old Greek man with chronic knee discomfort. The ganglionic cyst originated from the infrapatellar fat pad and had no intrasynovial extension. The final diagnosis was determined with magnetic resonance imaging of the knee, and the lesion was treated with surgery.ConclusionsThese lesions are asymptomatic in most cases but often are misdiagnosed as meniscal or ligamentous lesions of the knee joint. Nowadays, the therapeutic trend for such lesions is arthroscopic excision, but when there is a large ganglion, as in this case report, the treatment should be an open and thorough resection. This report is intended mostly but not exclusively for clinical physicians and radiologists.

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The diffusional behaviour of sorbic acid in model food gels is discussed. The apparent diffusivity (D,) of sorbic acid in a aqueous gel containing 1.5% w/w agar, when determined by monodimensional diffusion (infinite gel columns) was found to be 8.8,8.9 or 9.2 X 10-"' m2/sec at 25°C depending on the method of calculation (eye fitting, eye fitting graphical method or computerized fitting method) and 8.7X 10-'" m%ec when determined by tridimensional diffusion (gel cubes immersed into an appropriate solution).The two methods displayed a good agreement; the tridimensional diffusion method had slightly worse repeatability than the monodimensional method (coefficient of variation 5 10% instead of 5.5% for the infinite gel columns) but has the advantage of being simple and rapid (1-3 hr instead of 24 hr). For the tridimensional diffusion method, D, values of sorbic acid measured by inward and outward diffusion in gel cubes of different compositions were found to be not significantly different, which suggests an absence of partition effects between the immersion solution and the gel.D, values appear to be slightly dependent on the gelling agent concentration (1.5, 2.5 and 4% w/w agar) in gel containing 40% w/w glycerol and 60% water. D, values of sorbic acid decreased when the temperature decreased. An apparent activation energy of 18 KJ/mol was found for the diffusion of sorbic acid. This value was similar to the activation energy for the change in viscosity of the solution occluded in the gel network.D, values were influenced by the concentration of the diffusant, with a slight decrease when initial concentration of sorbic acid increased, following a linear relationship. The product D.r) when r ) is the viscosity of the solution occluded in the gel was approximately constant.

The diffusivity at infinite diffusant dilution (Do) of sorbic acid in high and intermediate moisture gels (with various substrates and water contents) and in three foods was evaluated. The determination of Do (25°C) was achieved by tridimensional diffusion in gels cubes o r by monodimensional diffusion in infinite food columns. For the same substrate concentration by weight, 0, values of sorbic acid in concentrated sugar solutions decreased slightly when the molecular weight of the sugar was increased. When a liquid substrate such as glycerol was used, Do values referred to equal concentrations by weight, were higher than in sugar solutions. The diffusion of sorbic acid is related, as a first approximation, to the water content rather than to the water activity of the diffusion medium.

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