Identification of Early Changes in Patellar Tendinopathy Using Ultra-high Field Strength MRI

This project will investigate patellar tendon tissue (transmission electron microscopy of structure and protein analyses) coupled with magnetic resonance imaging (1.5T and 7T) from persons with i) chronic patellar tendinopathy (CT), ii) the earliest possible signs and symptoms of patellar tendinopathy (ET), and iii) symptom free controls (CTRL)(matched for age and physical activity/sports participation).

The investigators hypothesize that 7T MRI will be able to detect more subtle changes in early tendinopathy as compared to 3T MRI, thereby taking advantage of the increased spatial resolution that can be obtained in MRI with higher field strength. Further the investigator hypothesise that alterations in the tissue will be more pronounced in the CT group compared to ET and healthy controls.

Tendon tissue plays an essential role in transmitting contractile forces to bone to produce movement and is therefore uniquely designed to withstand considerable loads (up to \~8 times body weight) during human locomotion. Yet, repetitive use often results in overuse injuries such as tendinopathies, which is a common clinical condition characterized by pain during activity, localized tenderness upon palpation, swelling of the tendon and impaired performance. Tendinopathy is a sizeable problem in both elite and recreational athletes. In fact, the incidence of tendon injuries has been estimated to be as high as 30-50% of all sports injuries, and 50% of elite endurance runners, and 6% of sedentary people will at some point experience a tendon injury. Moreover, the symptoms and reduction in performance may be quite protracted and last for years. To date the ability to detect the early onset of the disease, and thus to prevent it from becoming chronic and debilitating, remains an enigma and the investigators wish to bridge this gap in knowledge by studying patellar tendon tissue samples coupled with magnetic resonance imaging (3T and 7T)

Eligibility Criteria:
Inclusion Criteria:

Common for all groups

* Sports active individuals.
* Age \[18-45\] years old.
* BMI \[18.5-30\]

ET - group

* Symptom onset within 90 days at inclusion
* Clinical signs of patellar tendinopathy.
* Activity related pain in the patellar tendon.
* Palpation pain in the proximal part of the patellar tendon.
* At least one of the following three changes on the ultrasound scanning:

  * Thickening of the AP diameter on the symptomatic side.
  * Increased Power Doppler signal on the symptomatic side.
  * Hypoechogenic area corresponding to the symptomatic area of the tendon.

CT - group,

* Symptom onset \>90 days ago
* Clinical signs of patellar tendinopathy.
* Activity related pain in the patellar tendon.
* Palpation pain in the proximal part of the patellar tendon.
* At least one of the following three changes on the ultrasound scanning:

  * Thickening of the AP diameter on the symptomatic side.
  * Increased Power Doppler signal on the symptomatic side.
  * Hypoechogenic area corresponding to the symptomatic area of the tendon.

CTRL - group - Similar activity level as the two patient groups.

Exclusion Criteria:

Common for all groups

* Previous surgery in the knee on the ipsilateral side.
* Previous corticosteroid injection in the patellar tendon on the ipsilateral side.
* Smoking
* Known arthritis
* Known diabetes
* Known hypercholesterolemia
* Previous injections in the ipsilateral tendon.
* MRI contraindications

  * Ferromagnetic objects
  * Pregnancy
  * Lactation

ET - group

* Previous injuries in the patellar tendon on the ipsilateral side.
* Started systematized treatment.

CTRL - group

- Previous injuries in the patellar tendon on the ipsilateral side.