MR imaging of patients with lateral epicondylitis of the elbow (tennis elbow): importance of increased signal of the anconeus muscle.

OBJECTIVE: The purpose of this study was to determine what changes might be detected on MR images of patients with chronic lateral epicondylitis (tennis elbow) that could explain why some cases are resistant to therapy. SUBJECTS AND METHODS: Seven consecutive patients with chronic lateral epicondylitis were included. The diagnosis was based on symptoms and signs characteristic of the disease, as determined by each patient's orthopedic surgeon. Three volunteers with normal elbows were control subjects. All patients had MR imaging of the involved elbow, and control subjects had MR imaging of the nondominant elbow. Short tau inversion-recovery (STIR) MR imaging was chosen because of its sensitivity to changes in the water content of muscle and its suppression of the fat signal. The images were analyzed visually and on an MR workstation to measure the signal intensity of the elbow muscles.
RESULTS: In all seven patients, MR images showed increased signal intensity of the anconeus muscle. This increase in signal intensity was not observed in the control subjects, and to our knowledge it has not been reported previously.
CONCLUSION: Increased signal intensity of the anconeus muscle on MR images in patients with chronic lateral epicondylitis suggests involvement of the muscle. Increased signal intensity is seen with edema, granulation tissue, and inflammation, which may explain the findings in this study. Our results are inconclusive as to whether this increased signal intensity contributes to the chronicity of patient symptomatology or is associated with abnormal elbow motion because of the symptoms.