MR imaging of epicondylitis. 
To systematically evaluate the MR findings in patients with epicondylitis compared with asymptomatic volunteers.  We imaged 43 elbows: 24 with epicondylitis (22 lateral, 2 medial) diagnosed by clinical examination, and 19 in 16 normal volunteers.  MRI was performed at 1.5 T using axial T1-weighted, axial fat-saturated FSE, and coronal or sagittal Fast STIR sequences.  Two independent observers evaluated the images for intratendon signal, tendon thickening, periosteal reaction, fluid in the radial head bursa, and anconeus edema.  All 24 patients with epicondylitis had increased signal on fat-saturated FSE and Fast STIR images.  Twenty-two of these patients had increased intratendon T1 signal, and 19 had tendon thickening.  No patient demonstrated fluid in the radial head bursa or periosteal reaction.  Only two patients had subtle anconeus edema, while three patients unexpectedly had increased T2 signal within the involved epicondyle.  One asymptomatic volunteer (high-performance athlete) had increased T1 and T2 signal with tendon thickening.  An additional two asymptomatic volunteers had increased T1 signal only.  MRI of epicondylitis demonstrates tendon thickening with increased T1 and T2 signal, but these findings may be seen in a small minority of asymptomatic individuals.  Anconeus edema, previously demonstrated on MRI in epicondylitis, was only rarely found, and distension of the radial head bursa, surgically described, was not seen.  Increased marrow T2 signal within the involved epicondyle is occasionally seen.