@1.1 antero posterior Xray of the knee showing vertical thin spur directed upwards with a deformation of the internal part of the bone but without any cortical changes
@7.15 axial T1 sequence showing an hypo intense mass between muscle and bone
@10.17 coronal STIR sequence showing the hyper intense lesion along the femoral shaft ;
@9.15 Axial T1 with galolinium contrast agent and fat saturation showing the peripheral enhancement of the lesion.
“TUG” LESION with bursitis
It is not uncommon to encounter cortical irregularities in the distal femur at sites of muscle attachment due to chronic stress changes.
“Tug” lesions are usually asymptomatic and of importance only in that they should not be mistaken for a tumor even when occasionally symptomatic.
One common site of such a tug lesion is in the posterior medial distal femoral shaft at the insertion site of the adductor magnus muscle or medial head gastrocnemius muscle, which has been termed a periosteal, juxtacortical, or cortical desmoid.
It is usually seen in children and adolescents.
CHARACTERISTIC CLINICAL FEATURES AND RADIOLOGIC FINDINGS
On MR, there may be associated cortical irregularity, marrow edema, periosseous edema and as in this case bursitis that explains the pain.
Another common entity in the differential diagnosis is an osteochondroma, which on MRI can be easily differentiated from a tug lesion by the presence of a cartilage cap.
- Craigen M A, Bennet G C, MacKenzie J R, Reid R. Symptomatic cortical irregularities of the distal femur simulating malignancy. J Bone Joint Surg Br 1994; 76(5): 814-817
- Posch T J, Puckett M L. Marrow MR signal abnormality associated with bilateral avulsive cortical irregularities in a gymnast. Skeletal Radiol 1998; 27(9): 511-514