Heel pain (PHP) is a complex disorder that is poorly understood. In previous lessons in this series, Plantar Heel Pain Syndrome (PHPS) was introduced, the available literature on its risk factor assessment and treatment was explored, and a new management option was discussed. for Optimal management of PHPS necessitates examination of the anatomy underlying the calf and foot region in order to establish the relationship between PHP and related tissues. In this document, the musculoskeletal and fascial structures beneath the foot and ankle will be explored about:
- Previous theories about PHPS (including plantar fasciitis and heel spurs)
- A “new protocol” for PHPS management
Anatomical Structures Relevant to PHPS Theory
In this section, the anatomy will be discussed in conjunction with the two most prominent theories regarding PHPS: plantar fasciitis and calcaneal spurs.
Fascia is composed of connective tissue that forms a continuous network throughout the body.  It is a collagen-based tissue that attaches stably, imparts strength, envelops different organs, supports internal structures, envelops the entire muscle and each muscle Fibrous fascia can be classified as superficial deep visceral fascia or parietal fascia, often further classified according to anatomical location.  The thickness of the fascia varies from very thin and almost transparent to strong and thickened.
Figure 1. Plantar fascia
The fascia of the foot is composed of fibrous connective tissue whose function is to separate support and attach muscles.  It can also be divided into superficial fascia and deep fascia. On the plantar side, the superficial fascia is involved in the formation of the plantar fat pad, while A deep layer known as the plantar fascia plays an important role in maintaining the medial longitudinal arch of the foot. 
The plantar fascia (PF), also known as the plantar fascia, arises proximally from the medial tubercle of the distal calcaneus and widens as it progresses distally (figure 1).  At the distal end of the metatarsophalangeal joint, it divides into five fingers that slide to each toe. these fuses Each toe has a fibrous flexion sheath and a deep transverse metatarsal ligament before inserting at the base of the proximal phalanx.    In addition to supporting the longitudinal arch of the foot, the PF is also involved in the mechanism of transmitting propulsion Force and pressure on the foot during loading (shock absorption). 
Again, it is worth noting that PF is located distal to the commonly reported area of heel pain in PHPS, which raises the question of whether it is a causative factor in PHPS.
Figure 2. Windlass test
Microtrauma from overstraining of PF is often considered to be the source of pain in PHPS. The Windlass test has been proposed as an evaluation technique for the diagnosis of plantar fasciitis on the basis that passive elongation of the plantar fascia causes elongation of the plantar fascia The big toe can cause pain in the heel (Fig. 2).
This hypothesis was further investigated by Fessel et al.  who assessed the function of the PF during various phases of gait and concluded that the “windlass effect” supporting the arch is questionable due to the substantial muscular contribution supporting the longitudinal arch of (Figure 3).
Figure 3. Muscular support of the longitudinal arch
In the anatomical study of PF Stecco et al.  identified three parts of the PF – medial central and lateral – with the central part being the thickest. All dissections show :
- PF continues above the calcaneus with a thin band corresponding to the periosteum of the calcaneus
- This layer of PF surrounds the calcaneus and is continuous with the paratendin of the Achilles tendon
The continuity of collagen fibers between the PF and the Achilles tendon remains highly controversial and is still widely debated.  
Further microscopic studies revealed the presence of Pacini and Ruffini bodies within the PF, suggesting a role for PF innervation in proprioception as well as in the stability and control of foot movements. 
Stecco et al.  further raised the question of whether PF is indeed fascia or aponeurosis. These terms are often used interchangeably in various studies.
Fascia – tissue with multi-directional arrangement of collagen fibers Aponeurosis – tissue with unidirectional arrangement of collagen fibers
In their anatomical study, Stecco et al.  found that even though the collagen fibers of PF were mainly aligned in the proximal-to-distal longitudinal direction, various fibers were also oriented in vertical lateral and oblique directions. They concluded that the multilayered structure of this collagen Fibers are more typical in fascia, so the term “plantar fascia” is more appropriate for this tissue. 
Aside from the structure of PF, a more pressing question is whether PF is actually the source of pain reported in PHPS. There is currently no evidence of nociceptive nerve endings in PF itself. However, it is recommended that when doing long stretches For example, during a neurodynamic test, both fascia and nerve tissue will be stretched because the two systems are continuous in the body.  There is no doubt that neurodynamic testing not only loads the nervous system but also challenges non-neural structures .
Following this concept Copieters et al.  investigated the effect of neurodynamic tests (droop and straight leg raise [SLR]) on experimental pain perception to assess whether pressure on the fascia could act as a neurodynamic process Alternative explanations for changes in pain perception in test. They injected hypertonic saline into the tibialis anterior muscle of 15 asymptomatic volunteers to increase the tension of the fascia and performed SLR and sag neurodynamic testing while all other movements of the ankle were restrained and monitored (Fig. 4) . 
Figure 4. Effect of neurodynamic testing on experimental muscle pain perception 
Copieters et al  found no change in the perception of experimental pain with SLR and collapsed neurodynamic tests and concluded that these neurodynamic tests had no effect on pain perception when the pain was not of neural origin (Fig. 5).
Figure 5. Results of neurodynamic testing of pain perception 
These findings are supported by Coppieters et al.  in another study, which investigated whether any mechanical movement of fascia and nerves occurred during a modified SLR maneuver. They inserted gauges into the scitiotibial and plantar nerves and 8 embalmed PF Strain was measured on cadavers in a modified SLR test. They found that even though there was significant movement of the tibial nerve in the tarsal tunnel during the modified SLR tibial maneuver, no movement occurred in the PF (Fig. 6). 
Figure 6. Effect of modified SLR test on nerve and fascia 
The results of this study were surprising given the prolonged stretch of fascia. This brings us back to the question posed earlier, considering the causes of heel pain reproduced by two standard tests (heel raise and mini squat) (Fig. 7). Both heel bearing and Stretch on the fascia can be ruled out as a cause of PHP. 
Figure 7. Inference for standard tests to reproduce heel pain 
A summary of all evidence on the involvement of PF in PHPS collected during various lectures on heel pain support could only find thickening of PF in PHPS (Fig. 8). 
Figure 8. Summary of the evidence for the involvement of the plantar fascia in PHPS (- indicates no support in the literature and + indicates support in the literature) 
Plantar heel spurs have been widely recognized as the cause of plantar fasciitis, but whether they actually cause the symptoms of PHP remains controversial.  Considering previous reviews of risk factors for PHPS calcaneal spurs generally considered to be They are found incidentally because they are not located in the weight-bearing area of the heel and are also found in asymptomatic individuals.   Therefore, there is no clear link between the presence of calcaneal spurs and PHPS.
Anatomical structures associated with the “new protocol”
Consequently, many structures have been ruled out as possible sources of heel pain reproduced in the heel raise and mini squat tests. It is therefore necessary to consider whether the source of the pain is muscular (Figure 9)?
Figure 9. Possible sources of heel pain reproducible in clinical trials 
Four of the five layers of soft tissue in the foot do not cover the heel (Figure 10). Only the heel is superficially covered with a fat pad, which has little nociceptive innervation and has not been shown to be a source of heel pain.  Considering that all muscles start from The calf to foot bypasses the heel into the farther foot, the heel itself has no muscles and the muscular system can be eliminated as a source of PHP. Since there is no evidence of muscle as a source, only neural tissue remains to be considered (Figure 11). 
Figure 10. Five layers of soft tissue of the foot 
Figure 11. Reasoning for clinical testing of muscle as a source of PHP 
Before exploring the neural organization of the foot, it is worth reviewing the results of the pressure pain threshold test performed in PHPS by Saban and Masharawi . Their results showed that although the presentation and sensitivity of heel pain did not differ significantly between the People with PHPS and those without the distal medial heel is the most sensitive area of the heel.  When considering the neuroanatomy of the foot, it is worth noting that the entrances of the medial and lateral plantar nerves into the foot coincide with reported areas of the foot. Increased heel sensitivity (Fig. 12).
Figure 12. PPT test sensitivity and neuroanatomical similarity 
The tibial nerve passes through the fibrous tarsal tunnel before splitting into the medial and lateral plantar nerves.  During this part of its course, the tibial nerve is very superficial because it is wedged between the bone and the skin without other protection. Palpation of nerves can easily cause Paresthesia similar to palpation of the ulnar nerve at the elbow.  From here, the medial and lateral plantar nerves, the medial calcaneal branch of the tibial nerve, and the arteries and veins enter the foot near the medial calcaneal tubercle. 
Figure 13. Skin innervation of the foot 
The cutaneous innervation of the foot is innervated by a total of 7 different nerves (Fig. 13):
- Saphenous nerve (L3,4)
- Deep peroneal nerve (L4,5)
- Superficial peroneal nerve (L4, S1)
- Medial plantar nerve (L4,5)
- Lateral plantar nerve (S1,2)
- Medial calcaneal branch of the tibial nerve (S12)
- Sural nerve (S1,2)
With regard to PHPS, the nerve of greatest interest is the medial calcaneal nerve. The medial calcaneal nerve is one of the main branches of the tibial nerve and usually divides from the tibial nerve just below the medial malleolus around the tarsal tunnel area.  Start here It enters the heel medially and terminates in the heel skin, providing sensory innervation to the skin in the heel region (Fig. 14). 
Figure 14. Medial Calcaneal Branches of the Tibial Nerve
Other researchers have investigated the role of neural tissue in PHPS:
- Two studies using plantar nerve nerve conduction testing 
- A review explores heel pain of neurogenic origin 
David Butler  also noted a peripheral neurogenic contribution to some heel spurs from the medial calcaneal nerve or lateral plantar nerve.
“A heel spur is also a painful condition where the exact pain may not be replicated on a physical assessment, but there are clues in neurodynamic testing that something is not right. It could be an effect on range of motion. Minimal limitation or symptoms caused in terms of problem, but not The “good” side” – David Butler 
He further suggested a neurodynamic approach to treating PHPS, specifically combining SLR testing with ankle dorsiflexion/valgus. 
Two nerve conduction studies by Öztuna et al.  and Ross et al.  assessed the medial plantar nerve (MPN). Öztuna et al.  also studied the lateral plantar nerve (LPN), while Rose et al.  examined the medial calcaneal nerve (MCN) to see any differences in the nerve conduction between these nerves (Fig. 15).
Figure 15. Nerve conduction study of the plantar nerve 
Both studies reported impairment of nerve conduction in these nerves. Öztuna et al.  found differences in nerve conduction between people with and without PHPS and reported that 88% of participants had deficits in nerve conduction in MPN and LPN. rose etc.  found nerve conduction impairment in the MCN in 72% of the participants (Fig. 16).
Figure 16. Nerve conduction study results 
Ross et al.  further showed that the reduction in nerve conduction velocity was caused by pressure on the nerve somewhere as it traveled down the leg before reaching the foot/heel. This supports the findings of Coppieters et al.  that neural tissue involvement seen in PHPS Modified SLR neurodynamic testing with tibial nerve deviation. Also of interest, nerve blocks of the posterior tibial nerve have been suggested as a treatment option in individuals with severe PHP, further supporting neural involvement in PHP. 
The theory of tibial nerve compression requires further study of its course in the leg.  After exiting the popliteal fossa, the tibial nerve travels down the hind leg between the superficial and deep muscles of the calf that may place pressure on the calf nerve. In the study by Saban and Deutscher, these muscles were found to be stiff, noncompliant, and painful on manual palpation.  This suggests that these muscles may actually disrupt the conduction of nerves along their path (Fig. 17).  When looking at a Cross-sectional images of the calf clearly show how the nerves and muscles are intertwined, highlighting the potential for muscles to put pressure on the nerves (Figure 18).
Figure 17. Course of the Tibial nerve
Figure 18. Cross-sectional image of the calf
It is unclear when the first dysfunctions in this interplay between nerve and muscle occur. Done:
Foot pain ⇒ Patient walks differently ⇒ Muscle dysfunction ⇒ Nervous disorder
Or did it happen the other way around? While the sequence of events may still be unknown, there is clearly a cure available, and one that is backed by sound theories. The next course in this series will be devoted to new treatment options. protocol.
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