Mechanisms Behind Development of Tendinopathy: Early Structural, Inflammatory, Nociceptive and Clinical Changes in Recreational Runners

The investigators intend to study the development of tendinopathy in humans that enter a phase of relative overloading of their tendons. This will be done in a large cohort of individuals from whom the investigators have obtained basic data and tests. A percentage of these participants will develop overuse symptoms and in those the investigators will perform investigations that will identify the initial pathological changes in tendinopathy

Participants are included as soon as possible after diagnosis of either Achilles or patella tendinopathy because the investigators wish to investigate the early changes in tendinopathy. The hypothesis is, that at the early development of tendinopathy there will be a mismatch between matrix protein anabolic and catabolic pathways, and will be associated with a secondary upregulation of inflammatory and apoptotic markers in the tendon and result in hypervascularization and hyper-metabolism.

Recruiting participants will be done in collaboration with local athletic clubs in the Copenhagen area. The athletic clubs include Sparta, Københavns Idræt Forening (KIF), Frederiksberg Idræt Forening (FIF). Furthermore, the investigators will establish contact through online social media such as Facebook, Twitter and Google. In addition, Information leaflets will be handed out, and medical staff at the emergency rooms repeatedly informed about the project. Healthy participants can be directly recruited by participants already in the project, social medias and through information leaflets handed out. It is planned to inform staff at the emergency rooms at Bispebjerg Hospital, Amager Hospital, Gentofte Hospital, Herlev Hospital and Hvidovre Hospital. Patients and healthy controls can contact the primary investigator directly through email or telephone.

Recruitment to project TESINaC will focus onset of exercise pain and every participant will be evaluated by a doctor if the participant have tendinopathy or not. Once included the participant will undergo following procedures as soon as possible after diagnosis is given:

• Questionnaire regarding training history and ongoing symptoms
• Ultrasound scanning of tendons
• Ultrasound isometric
• Blood samples
• MRI of tendons on both legs MRI precedes biopsy as it can identify any diseased area within the tendon from which a biopsy can be taken. Only participants with tendinopathy will have to undergo biopsy from both patella tendons once during the project. Healthy participants will not undergo biopsy. No biopsy will be taken from the Achilles tendon as this procedure may worsen the participants symptoms.