Heel pain is a common presenting symptom in daily practice. Although there are many causes in the etiology of heel pain, mechanical causes are the most common. The location of the pain can guide the clinician to the proper diagnosis. Plantar fasciitis (PF) and calcaneal spur are usually the fi rst diagnoses that come to mind when the differential diagnosis of heel pain is made. However, since the trigger points of the muscles in the plantar region of the foot are not given due importance, they are not considered in the diagnosis. The cause of PF remains unknown. Simons et al. [1] hypothesized that the presence of myofascial trigger points in the plantar intrinsic foot musculature and proximal foot muscles could play a significant role in plantar heel pain. Just like plantar fascia, the quadratus plantae (QP) and the fl exor digitorum brevis (FDB) muscle contributes to the arch of the foot and its biomechanics [2]. Rest, prescription of nonsteroidal anti-infl ammatory medications, foot taping, physical therapy, stretching exercises, and steroid injection are current traditional therapies. Dry needling and acupuncture are alternative and minimally invasive trigger point stimulation techniques. It has been observed that dry needling can modify the metabolic environment surrounding a trigger point and decrease spontaneous electrical activity in trigger point regions of skeletal muscle [3].

Sometimes, there is no response to the treatment in patients who receive steroid injections with the diagnosis of PF or calcaneal spur. In such cases, myofascial trigger points in the plantar muscles may be the source of pain. Before diagnosing PF or calcaneal spur in patients with heel pain, investigation of myofascial trigger points, which is a more common pathology, should be kept in mind. Trigger points in this muscle may be more frequently detected when viewed from the perspective of myofascial pain syndrome. In this region, myofascial pain syndrome can sometimes be seen as a primary pathology and sometimes as an entity accompanying the primary pathology. It is a more accurate approach to use ultrasound guidance instead of anatomical landmarks in terms of the effect of the treatment so that trigger point injections can be made in the right place in the plantar muscles [4].

Ultrasound technology, which has become an indispensable tool in the preliminary diagnosis, differential diagnosis, and treatment processes in musculoskeletal system pathologies, has become a stethoscope for physicians interested in these fields [5]. Shear wave elastography (SWE) is an ultrasonographic screening technique that permits noninvasive estimate of the muscle’s elasticity. Based on the fact that hard tissue allows for less tissue displacement than soft tissue, the elastic characteristics are assessed by the propagation velocity. Various tissues, including the gastrocnemius muscles, quadriceps muscle, peroneus longus, tibialis anterior, and patellar tendon, have been evaluated with SWE. In addition, gray-scale ultrasonography can determine architectural plantar fascia properties such as shape and thickness [6]. In a study by Zhou et al. [7], a link between the stiffness of the medial gastrocnemius and the severity of pain in persons with PF is established. Greater rigidity of the medial gastrocnemius may be indicative of increased discomfort in PF patients. In clinical practice, muscular stiffness is a good sign for patients with PF. Patients with PF should focus their muscle-releasing and stretching activities on the linked muscle for prevention and recovery [7].

Three topics are essential in ultrasound-guided intervention, which includes aiming at the right point, minimizing possible complications, and providing safety to the physician and the patient in medicolegal issues. Many conventional and invasive techniques have been used to treat PF. In the literature, there are studies in which extracorporeal shock wave therapy is performed under ultrasound guidance, and injection techniques and treatments are monitored with ultrasonographic parameters [8]. There are also studies referring to the importance of myofascial trigger points of the intrinsic muscles (QP, FDB, abductor hallucis) and proximal muscles of the foot (gastrocnemius, soleus, tibialis posterior) in the treatment of heel pain (Figure 1) [9,10]. When the QP and FDB muscle, which has a critical role in this region, is considered for intervention or the adjacent plantar fascia is targeted for treatment, care should be taken not to damage neurovascular structures (Figure 2).

In conclusion, the use of ultrasound (and, if applicable, elastography) in the diagnosis of heel pain is cost-effective and reliable. It can guide PF injection and prevent possible complications against neurovascular structures in this region. In addition, it should be kept in mind that patients with PF may have active trigger points in the muscles located in the plantar region of the foot or leg. Hence, treatment for these active trigger points should be added to the treatment algorithm.

Figure 1. Pain (Red) Referred From Trigger Point (X) in the Leg and Foot Muscles

Images show trigger points and referred pain zones in the abductor hallucis (A), quadratus plantae (B), flexor digitorum brevis (C), soleus (D),
medial head of gastrocnemius (E), and tibialis posterior (F).