In vivo [Formula: see text] MR spectroscopy using 3 Tesla to investigate the metabolic profiles of joint fluids in different types of knee diseases

In vivo proton ([Formula: see text]) magnetic resonance spectroscopy (MRS) has not yet been systematically used to study joint fluids in human knees. The objective of this study, therefore, was to assess the ability of proton MRS to identify the apparent heterogeneous characteristics of metabolic spectra in the joint fluid regions in human knees using a high‐field MRI system. Eighty‐four patients with effusion lesions who were referred for routine knee MR imaging underwent proton MRS with point‐resolved, single‐voxel MR spectroscopy using a clinical 3.0 Tesla MRI system. Thirty‐eight patients were confirmed to have the following: degenerative osteoarthritis, 21 patients (Group 1); traumatic diseases, 12 patients (Group 2); infectious diseases, 4 patients and an inflammatory disease, 1 patient (Group 3). Spectroscopy data were analyzed using the public jMRUI freeware software to obtain lipid metabolites. Nonparametric statistical comparisons were performed to investigate any differences in metabolites among the three disease groups. The major metabolites were vinylic [Formula: see text] lipids around [Formula: see text] , [Formula: see text] lipids around [Formula: see text] , and [Formula: see text] lipids around [Formula: see text]. Each patient had either a [Formula: see text] lipid peak, [Formula: see text] and [Formula: see text] lipid peaks, or all three peaks. There were no significant differences among the three groups for the [Formula: see text] ([Formula: see text]), [Formula: see text] ([Formula: see text]), and [Formula: see text] lipids ([Formula: see text]) and water ([Formula: see text]); none of the metabolites could differentiate between any of the three types of diseases. The [Formula: see text] lipids in the 38 patients who had confirmed fluid characteristics were significantly correlated with [Formula: see text] lipids ([Formula: see text] , [Formula: see text]). The ratio of [Formula: see text] to [Formula: see text] was highest in the degenerative disease. In both the degenerative and traumatic diseases, metabolite peaks of the vinylic [Formula: see text] lipids around [Formula: see text] and of the sum of the [Formula: see text] and [Formula: see text] lipids around [Formula: see text] were observed, but in the infectious disease, only a metabolite peak of the sum of the [Formula: see text] and [Formula: see text] lipids was detected. Although none of the metabolites could statistically significantly differentiate between the three types of diseases, the different lipid metabolite peaks and their ratios in the three disease groups may give us a hint at the different mechanisms of joint fluids in the infectious, degenerative, and traumatic diseases. PACS number(s): 87.61.Ff, 33.25.+k, 87.14.Cc