Plantar heel pain is commonly encountered by clinicians. Various conditions, such as plantar fasciopathy, myofascial syndrome and entrapment of the tibial, plantar and calcaneal nerves at the tarsal tunnel can cause plantar heel pain. This diversity in aetiology makes the diagnosis and treatment challenging. There are limited studies on pain mechanisms in patients with planter heel pain. There is no gold criterion standard for the diagnosis. Although various interventions have been reported, no specific treatment approach has yet been identified as being most effective. The first aim of this thesis was to critically appraise the literature on plantar heel pain of neural origin. Various databases were searched for peer-reviewed articles that predominantly focused on neurogenic plantar heel pain or that discussed relevant biomechanics of the tibial, plantar and calcaneal nerves. This review revealed inconsistency in the literature regarding the diagnosis and treatment of neurogenic plantar heel pain. There also was a lack of evidence for treatment approaches although the majority of patients with plantar heel pain are reported to improve with conservative treatment. The second aim of this thesis was to examine the biomechanical effects of clinical tests and combination of movements on various structures associated with plantar heel pain. This aim was achieved through cadaver studies (Study 1–3), in which strain in the plantar fascia and the nerves of the lower limb, and excursion of the nerves were measured during various movements and positions of the lower limb. Study 1 examined the Dorsiflexion-eversion test used to diagnose tarsal tunnel syndrome (TTS) and the Windlass test for plantar fasciopathy given the similarity between both tests. Both the Dorsiflexion-eversion and Windlass tests significantly increased strain in the structures that are commonly associated with plantar heel pain (the tibial and plantar nerves and plantar fascia). This suggests that the usefulness of the Dorsiflexion-eversion and Windlass tests in the differential diagnosis of plantar heel pain might be limited. Study 2 investigated the influence of different positions in adjacent joints on nerve biomechanics during ankle and toe movement. Increased strain in the tibial nerve at the ankle and plantar nerves associated with ankle and toe movement was significantly higher when the nervous system was pre-tensioned at a more proximal joint. Strain was even higher when the nerve bed was pre-tensioned at two joints. Study 3 examined a modified straight leg raising (SLR) test in which ankle dorsiflexion is performed before hip flexion. This test has been suggested to diagnose distal neuropathies such as TTS. During the modified SLR, the excursion and strain in the sciatic nerve associated with hip flexion were transmitted distally along the nerve from the hip to the foot. As a result, the strain in the nerves around the foot and ankle increased significantly during hip flexion. This movement did not affect plantar fascia strain. Consequently, the modified SLR may be a useful test to differentially diagnose plantar heel pain. This test warrants future research to evaluate its clinical use in patients with neurogenic plantar heel pain. The third aim of this thesis was to determine the reliability of high-resolution ultrasound for measuring the cross-sectional area of the tibial nerve at the tarsal tunnel and to compare the tibial nerve size between people with and without plantar heel pain. Study 4 investigated intra and intertester reliability in 10 participants without plantar heel pain by calculating intraclass correlation coefficients, measurement error and smallest detectable difference (SDD). Intra and intertester reliability were excellent, with very small measurement error and SDD. Tibial nerve enlargement in an individual patient by as little as 1.8 mm2 can be detected reliably with high-resolution ultrasound. The use of average value of three scans is recommended to compare between the involved and uninvolved side. Differences in the nerve size between 26 patients with plantar heel pain and 20 control participants were also analysed. There was no significant difference in tibial nerve size between both groups. Future research is needed to investigate the tibial nerve size in patients with proven TTS using ultrasonography. The fourth aim of this thesis was to investigate the characteristics of plantar heel pain through Study 5 for the same group of patients and control participants as in Study 4. Several self-report measures on pain and quality of life were used. Clinical tests and quantitative sensory tests (QST) were performed at local and remote sites on the involved and uninvolved side in the patients and on one side in the control participants. In the patients, mechanical hyperalgesia was the main finding as demonstrated by changes in palpation and pressure pain threshold. Other findings were changes in current thresholds, vibration threshold and thermal perception thresholds. These results suggest the existence of sensory changes that likely indicates change in peripheral and central pain processing. It is recommended to utilise a multidimensional pain assessment for patients with plantar heel pain. The findings in this thesis are important for the diagnosis and treatment of plantar heel pain. For future research, the results suggest to use fresh cadavers when investigating biomechanics of the clinical tests and nerve gliding exercises that are used for patients with plantar heel pain. It is also suggested to evaluate the cross-sectional area of the tibial nerve at the tarsal tunnel, the QSTs and all other diagnostic measurements in this thesis in patients with neurogenic plantar heel pain or patients with TTS.

Bakgrund En vanlig orsak till smärta i fötterna är plantar fasciit och som kan enkelt förklaras som överbelastning av plantarfascian. Smärtan är lokaliserad anteriort på calcaneus och smärtan provoceras vid stående och gående. Aktivitetsanpassningar, kortisoninjektioner, stretching och sulor är vanliga behandlingsåtgärder vid plantar fasciit. Plantarfascian tillsammans med muskulatur kontrollerar fotvalvets rörelser och stabilitet. I dagsläget finns det en kunskapslucka kring vilka effekter muskelstärkande träning har på besvär i samband med plantar fasciit.   Syfte Syftet med denna systematiska litteraturöversikt var att undersöka vilka träningseffekter som finns för träning av lokal- och global fotmuskulatur hos personer med plantar fasciit.   Metod Den systematiska litteraturöversikt utfördes genom sökning i databasen Pubmed. Söksträngen utformades utifrån de inklusionskriterier som artiklarna behövde uppfylla. Granskning av artiklar och bedömning av bias utfördes enligt SBU:s formulär ”Bedömning av randomiserade studier”.   Resultat Fem randomiserade kontrollerade studier (RCT) uppfyllde inklusionskriterierna. De inkluderade studierna bestod av studier där en av interventionerna var muskelstärkande träning för fotmuskulatur. De effekter som upptäcktes i studierna var minskad smärta, förbättrad funktion, förändringar av plantarfascian och förändringar i gångmönstret.   Konklusion De fem studier som finns i området visar på en tendens att muskelstärkande träning har en positiv påverkan att lindra besvär i samband med plantar fasciit. I dagsläget behövs betydligt mer forskning för att kunna fylla kunskapsluckan av vilka effekter muskelstärkande träning för fotens muskulatur har på plantar fasciit.