From the Research
To locate the posterior tibialis muscle on ultrasound, position the patient lying down with their leg slightly externally rotated and place the ultrasound probe on the medial aspect of the lower leg, approximately one-third of the way down from the knee, oriented in a transverse plane, as this approach has been validated by recent studies 1, 2. The posterior tibialis appears as a pennate muscle deep to the soleus and medial to the fibula, with a characteristic triangular or oval shape on cross-section and a fibrillar echotexture. For optimal visualization, start at the medial malleolus and follow the tendon proximally until it transitions into muscle belly. Use a linear transducer (7-12 MHz) for superficial scanning or a curvilinear probe for deeper structures in larger patients, as recommended by studies 3, 4. Apply sufficient gel and maintain light pressure to avoid compressing the structures. Color Doppler can help identify nearby neurovascular structures including the posterior tibial artery and tibial nerve, which run alongside the muscle. Dynamic examination during ankle inversion against resistance can confirm identification by observing muscle contraction. This technique is useful for evaluating muscle tears, tendinopathy, or other pathologies affecting this important ankle invertor and foot arch supporter, and has been supported by recent research 5, 2. The most recent and highest quality study 2 suggests that needle placement into the TP muscle can be accurately performed with ultrasound guidance, with a mean distance from the needle to the tibial nerve and posterior tibial artery of 10.0 + 4.7 mm and 10.2 + 4.7 mm respectively. The superficial border of the TP muscle from the skin was at a mean depth of 25.8 + 4.9 mm, providing a reliable reference for needle placement. Some key points to consider when locating the posterior tibialis muscle on ultrasound include:
- The muscle is located deep to the soleus and medial to the fibula
- The muscle has a characteristic triangular or oval shape on cross-section and a fibrillar echotexture
- The use of a linear transducer (7-12 MHz) or a curvilinear probe for deeper structures in larger patients
- The application of sufficient gel and maintenance of light pressure to avoid compressing the structures
- The use of color Doppler to identify nearby neurovascular structures
- The performance of dynamic examination during ankle inversion against resistance to confirm identification by observing muscle contraction.