Keywords:
Congenital, Normal variants, Diagnostic procedure, MR, Musculoskeletal soft tissue, Extremities, Anatomy
Authors:
K. Pikoulas, I. Staikidou, G. Giannikouris, G. Mantzikopoulos, C. Kokkinis; Athens/GR
DOI:
10.1594/essr2018/P-0002
Conclusion
In cases where a mass lesion is shown between the iliotibial band and the lateral femoral condyle,
the radiologist should carefully compare the signal intensity of the mass with that of muscle tissue,
and follow its entire length to ensure that it is inserted into the iliotibial band anteriorly and blends with the native plantaris muscle posteriorly,
in order to report it as an accessory plantaris muscle.
The presence and the volume of the accessory plantaris muscle between the two sides of the body can be variable (fig.2) and can even present with two bellies (fig.3).
Constant findings in all accessory plantaris muscles include an ellipsoid shape in the coronal plane and an anterior insertion below the vastus lateralis muscle.
In our study the accessory plantaris muscle wasn't mentioned in the radiologic report in about half of the cases.
However,
this fact had no consequences in patient's treatment.
In conclusion,
the presence of the accessory plantaris muscle seems to be an incidental finding in knee MR examinations.
Though,
recognition of its presence may have some effects in two cases: first,
when an ACL reconstruction is planned,
care should be taken not to injure the accessory plantaris muscle [fig.4],
and second,
the ability of the adipose tissue,
interposed between the iliotibial band and the lateral femoral condyle,
to act as a lubricant during flexion of the knee,
is restricted by the presence of the accessory plantaris muscle,
and this could facilitate an earlier initiation of the iliotibial band friction syndrome [fig.7].