Gastrocnemius tendinosis--A frequent finding on MRI knee examination

Gastrocnemius tendinosis (GT) is one potential cause for posterior knee pain, commonly overlooked on clinical examinations and imaging. This study assesses the frequency of GT on MR imaging in a convenience sample based on a database search and associations with other articular pathologies and clinical findings.

With IRB approval, retrospective review was completed on 300 randomly selected MR knee exams performed from February 2009 to June 2010. Following de-identification, axial T2 and sagittal PD images, with or without fat suppression, were reviewed by 2 radiologists. The gastrocnemius tendon femoral attachments were graded as normal, mild (few cysts, thickening, intermediate signal) or severe GT (multiple cysts, marrow edema, tear). Select associated MR findings of internal derangement were documented. Clinical charts were reviewed for clinical presentation, physical exam findings, and select demographics.

The inter-observer reliability for presence/grading of GT was very high (kappa statistic=0.97). Frequency of GT was 50.33%, most frequently involving medial head of gastrocnemius (63.6%). Grades of GT were 41.7% and 17.2% for mild and severe respectively. Univariate analysis showed statistically significant relationship between grade of GT with arthrosis (p=0.05) and clinical joint effusion (p=0.02). Multivariate analysis showed higher odds of severe GT for individuals with medial plus lateral GT. Statistical significance was noted for presence of both GT and ACL tear (13.9%; p=0.02).

Significant findings of our analysis included GT presented with predominant involvement of medial head of gastrocnemius tendon, mild in severity, strong association with ACL tear, presented frequently as posterior knee pain, limited joint motion and clinical joint effusion. However, there was no statistically significant association between demographic features and medical comorbidities in the patients. Increased understanding of frequency of GT allows more accurate reporting of MR knee exam and systematic search for associated abnormalities.