Øystein Bjerkestrand Lian On the causes of patellar tendinopathy Faculty of Medicine University of Oslo 2007 Table of contents Table of contents ............................................................................... I Acknowledgements............................................................................IV List of papers ...................................................................................VI Definitions ..................................................................................... VII Summary ...................................................................................... VIII Introduction .....................................................................................1 Anatomy ........................................................................................1 Gross anatomy...................................................................................... 1 Vascular supply..................................................................................... 1 Cell components ................................................................................... 2 Innervation.......................................................................................... 2 Physiology ......................................................................................3 Pathology.......................................................................................4 Histopathology ..................................................................................... 4 Cell pathology ...................................................................................... 5 Vascular pathology ................................................................................ 6 Healing processes .................................................................................. 7 Pain mechanisms ................................................................................... 7 Diagnosis of patellar tendinopathy ........................................................7 Epidemiology of jumper’s knee ............................................................9 Intrinsic risk factors for patellar tendinopathy ........................................ 10 Gender .............................................................................................. 11 Antropometric data, strength and flexibility ................................................ 11 Leg length and patellar position ............................................................... 12 Patellar impingement ............................................................................ 14 Extrinsic risk factors for patellar tendinopathy........................................ 15 Training load....................................................................................... 15 Floor hardness ..................................................................................... 15 Methodological considerations............................................................ 16 Study aims ................................................................................... 18 I Methods......................................................................................... 20 Interview and clinical examination ...................................................... 20 Study populations and interviews.............................................................. 20 Diagnostics ................................................................................... 22 Standard form ..................................................................................... 22 Biomechanical testing...................................................................... 23 Ultrasound examination ................................................................... 24 Immunehistochemistry..................................................................... 26 Surgical technique ................................................................................ 26 Biopsy procedure.................................................................................. 26 Nerve staining and analyses..................................................................... 26 Immunohistochemistry ........................................................................... 26 Semi-quantitative analysis ...................................................................... 27 Apoptosis assessment ...................................................................... 28 Light microscopic appearance .................................................................. 28 Detection of apoptosis and assessment of caspase activation ............................ 28 Image analysis ..................................................................................... 28 Ethics ......................................................................................... 29 Statistics ..................................................................................... 29 Results and discussion ....................................................................... 30 Prevalence data............................................................................. 30 Results .............................................................................................. 30 Discussion .......................................................................................... 33 Gender........................................................................................ 35 Results .............................................................................................. 35 Discussion .......................................................................................... 35 Antropometrical data ...................................................................... 36 Results .............................................................................................. 36 Discussion .......................................................................................... 36 Sports history and training background ................................................. 37 Results .............................................................................................. 37 Discussion .......................................................................................... 38 Biomechanical data......................................................................... 39 II Results .............................................................................................. 39 Discussion .................................................................................... 41 Ultrasound data ............................................................................. 44 Results .............................................................................................. 44 Tendon changes observed by ultrasonography ............................................... 45 Discussion .......................................................................................... 46 Innervation................................................................................... 49 Results .............................................................................................. 49 Microscopy ......................................................................................... 50 Immunohistochemistry ........................................................................... 50 Sensory nerves..................................................................................... 50 Sympathetic nerves............................................................................... 50 General nerve occurrence ....................................................................... 51 Semi-quantitative immunohistochemistry.................................................... 51 Discussion .......................................................................................... 51 Apoptosis ..................................................................................... 52 Results .............................................................................................. 52 Discussion .......................................................................................... 53 A model for the causation of patellar tendinopathy .................................. 56 Tissue homeostasis model ....................................................................... 56 Risk factor model ................................................................................. 57 Inciting event ...................................................................................... 59 Mechanotransduction............................................................................. 60 Conclusions .................................................................................. 61 References ..................................................................................... 63 III Acknowledgements This study was carried out at Oslo Sports Trauma Research Center, located at the Norwegian University of Sports and Physical Education, Oslo, Norway. I would like to thank this institution for the opportunity to carry out the research. I would like to express my sincere gratitude to everyone who has been involved in this thesis project, directly or indirectly. In particular I would like to thank: Roald Bahr, MD, PhD, professor and chair of the Oslo Sports Trauma Research Center and Department for Health Studies, Norwegian University of Sports and Physical Education, and my main tutor, for the opportunity to study at the Oslo Sport Trauma