The investigators want to inject insulin-like growth factor-I (IGF-I) into the patella tendon of Ehlers-Danlos patients and healthy controls to evaluate the response in collagen synthesis. Furthermore collagen synthesis is measured in muscle connective tissue and in skin.

The hypothesis is that the connective tissue in Ehlers-Danlos patients is more compliant and poorer in collagen than healthy controls, but that collagen synthesis can be stimulated by IGF-I.

IGF-I will be injected with ultrasound guidance to one patella tendon and the other one will be injected with saline as control. Injections will be performed double blinded and timed 24 hours and 6 hours before tissue sampling.

Collagen synthesis will be measured as fractional synthesis rate based on stabile isotope technique using labelled proline.

10 patients diagnosed with Classical form of Ehlers-Danlos syndrome will be included and matched with 10 healthy controls based on age, gender, BMI and activity level.

The muscle biopsy will be taken from vastus lateralis muscle and the skin biopsy from the buttocks. The biopsies will if the size permits it also be used for histology and mRNA analyses.

Inclusion Criteria:

• Classic form of Ehlers-Danlos syndrome OR healthy matched control

Exclusion Criteria:

• Malignity, cardiac diseases, diabetes, tendinopathy in patella tendons