This prospective clinical cohort study will follow 40 patients who recieve botulinum toxin A treatment for proximal medial gastrocnemius tightness with subsequent Chronic Plantar Fasciitis for two years. Three injections of botulinum toxin (75IU) will be administered with intervals of three months. Participants will be followed at baseline, 3 months, 6 months, 1 year and 2 years with Patient Related Outcome Measures (PROMS) and physical test (Ergotest and ankle dorsiflexion).

The connection between gastrocnemius tightness and plantar fasciitis has been demonstrated in several clinical studies. Patients with chronic pathology, and unsatisfactory results from physical therapy, may benefit from gastrocnemius lengthening. This is usually obtained with proximal medial gastrocnemius recession surgery (PMGR), but recent studies and recent experience from our hospital suggest that similar effect may be obtained with ultrasound guided- injections of Botulinum Toxin A injections in the proximal medial gastrocnemius muscle.

This study will follow patients with gastrcnemius tightness (demonstrated by the Silferskiolds test) and subsequent chronic (MRI-verified) plantar fasciitits who has not recieved satisfactiory results from at least three months of guided physcial therapy.

Participants will recieve three ultrasound guided injections of 75IU of Botulinum Toxin A with three month intervals.

They will be followed with clinical controls for two years after the first injection.

THe main outcome is the Manchester Oxford Foot Questionnaire (MOxFQ).

Inclusion criteria:

1. Age 18-75 years.
2. An isolated gastrocnemius contracture must be verified with the Silfverskiölds test before inclusion.
3. Diagnosis plantar fasciitis verified clinically by an orthopaedic surgeon.
4. Diagnosis verified by MRI. MRI criteria: Thickening of the plantar fascia, oedema in the calcaneus, pathological signal changes in the plantar fascia (35)
5. Duration of symptoms must be at least 12 months prior to first BTA injection.
6. Conventional Physical Therapy must have been tried at least three months without a significant reduction of symptoms in the affected foot.

Exclusion criteria:

1. Previously undergone surgery for plantar fasciitis.
2. Patients with severe talocrural pathology or serious malalignment of foot and ankle
3. Severely reduced peripheral circulation
4. History of alcoholism, drug abuse, psychological or other emotional problems likely to jeopardize informed consent.
5. Patients with a contraindication/non-compliance for MRI examination.
6. History of allergic reaction/anaphylactic reaction or other contraindication to botulinum toxin.
7. Not able to read and/or speak a Scandinavian language or English adequately.

The population consists of patients who recieve routine care at our hospital.