Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

O estudo busca determinar fatores predisponentes para osteoartrite do quadril, por meio da avaliação de parâmetros radiográficos nos quadris de indivíduos idosos. Foram realizadas medições em radiografias de 106 indivíduos com idade acima de 60 anos, sendo um grupo com osteoartrite do quadril e um segundo grupo de indivíduos sem osteoartrite (grupo controle). As incidências radiográficas utilizadas foram ântero-posterior da pelve em ortostase, falso perfil de Lequesne e Dunn a 45 graus de flexão do quadril. Após aplicação de critérios de seleção bem definidos para osteoartrite primária do quadril, o número de quadris avaliados foi 112 quadris de indivíduos normais e 72 quadris de indivíduos com osteoartrite. Os parâmetros radiográficos estudados foram ângulo centro-borda de Wiberg, ângulo de Tönnis, índice acetabular de profundidade por diâmetro, percentual de cobertura da cabeça do fêmur, ângulo colo-diafisário, ângulo centro-borda anterior, offset entre a cabeça e o colo do fêmur, ângulo alfa, esfericidade da cabeça do fêmur e versão do acetábulo. As medidas radiográficas ângulo colo-diafisário, ângulo alfa, índice acetabular de profundidade por diâmetro e percentual de cobertura da cabeça do fêmur apresentaram valores médios significativamente diferentes nos pacientes com osteoartrite primária, quando comparados aos do grupo controle, sugerindo serem fatores predisponentes para a osteoartrite do quadril / This study aimed to determine factors that predispose towards hip osteoarthritis, by means of evaluating the radiographic parameters of elderly individuals hips. Radiographic measurements were made on 106 individuals aged 60 years or over: one group with hip osteoarthritis and another group of individuals without osteoarthritis (control group). The radiographic views used were the antero-posterior view of the pelvis in orthostatic position, Lequesnes false profile and Dunns view with 45 degrees of hip flexion. After applying well-defined selection criteria for primary osteoarthritis of the hip, the numbers of hips evaluated were 112 hips from normal individuals and 72 hips from individuals with osteoarthritis. The radiographic parameters studied were the Wiberg center-edge angle, Tönnis angle, acetabular index of depth to diameter, percentage coverage of the femoral head, neck-shaft angle, anterior center-edge angle, femoral neck-head offset, alpha angle, sphericity of the femoral head and acetabular version. The radiographic measurements of the neck-shaft angle, alpha angle, acetabular index of depth to diameter and percentage coverage of the femoral head presented mean values that were significantly different between the patients with idiopathic osteoarthritis and the control group. This suggests that these factors may predispose towards hip osteoarthritis

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 5 uppsatser.

O estudo busca determinar fatores predisponentes para osteoartrite do quadril, por meio da avaliação de parâmetros radiográficos nos quadris de indivíduos idosos. Foram realizadas medições em radiografias de 106 indivíduos com idade acima de 60 anos, sendo um grupo com osteoartrite do quadril e um segundo grupo de indivíduos sem osteoartrite (grupo controle). As incidências radiográficas utilizadas foram ântero-posterior da pelve em ortostase, falso perfil de Lequesne e Dunn a 45 graus de flexão do quadril. Após aplicação de critérios de seleção bem definidos para osteoartrite primária do quadril, o número de quadris avaliados foi 112 quadris de indivíduos normais e 72 quadris de indivíduos com osteoartrite. Os parâmetros radiográficos estudados foram ângulo centro-borda de Wiberg, ângulo de Tönnis, índice acetabular de profundidade por diâmetro, percentual de cobertura da cabeça do fêmur, ângulo colo-diafisário, ângulo centro-borda anterior, offset entre a cabeça e o colo do fêmur, ângulo alfa, esfericidade da cabeça do fêmur e versão do acetábulo. As medidas radiográficas ângulo colo-diafisário, ângulo alfa, índice acetabular de profundidade por diâmetro e percentual de cobertura da cabeça do fêmur apresentaram valores médios significativamente diferentes nos pacientes com osteoartrite primária, quando comparados aos do grupo controle, sugerindo serem fatores predisponentes para a osteoartrite do quadril / This study aimed to determine factors that predispose towards hip osteoarthritis, by means of evaluating the radiographic parameters of elderly individuals hips. Radiographic measurements were made on 106 individuals aged 60 years or over: one group with hip osteoarthritis and another group of individuals without osteoarthritis (control group). The radiographic views used were the antero-posterior view of the pelvis in orthostatic position, Lequesnes false profile and Dunns view with 45 degrees of hip flexion. After applying well-defined selection criteria for primary osteoarthritis of the hip, the numbers of hips evaluated were 112 hips from normal individuals and 72 hips from individuals with osteoarthritis. The radiographic parameters studied were the Wiberg center-edge angle, Tönnis angle, acetabular index of depth to diameter, percentage coverage of the femoral head, neck-shaft angle, anterior center-edge angle, femoral neck-head offset, alpha angle, sphericity of the femoral head and acetabular version. The radiographic measurements of the neck-shaft angle, alpha angle, acetabular index of depth to diameter and percentage coverage of the femoral head presented mean values that were significantly different between the patients with idiopathic osteoarthritis and the control group. This suggests that these factors may predispose towards hip osteoarthritis

No description available.

O presente estudo destinou-se a realizar uma análise comparativa entre a osteoartrite de quadris e o posicionamento acetabular através de exames radiográficos e de tomografia computadorizada. Foram incluídos 13 pacientes portadores e oito não-portadores de osteoartrite primária do quadril, recrutados no Ambulatório do Instituto de Ortopedia e Traumatologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. Os exames foram submetidos à medição das seguintes variáveis: ângulos acetabulares, ângulo centro-borda, sinal do entrecruzamento, largura e profundidade do acetábulo no RX; anteversão e ângulos setoriais acetabulares nos tomogramas. Não se verificou diferença estatisticamente significatova na anteversão acetabular entre ambos os grupos, ao passo que o ângulo acetabular setorial posterior mostrou média inferior no grupo afetado / The present study intends to develop a comparative analysis between primary hip osteoarthritis and acetabular positioning through x-ray exams and computed tomographic scans. 13 affected and 8 non-affected patients by degenerative hip disease with no underline causes are recruited within the ambulatory care service of the Institute of Orthopedics and Traumatology of the Hospital of Clinics, São Paulo University Medical School. Their radiographic exams are studied for extracting some parameters named as: acetabular angles, center edge angle, crossover sign, acetabular width and acetabular depth. Tomographic films give information to measure acetabular ante version and acetabular setorial angles. Statistically, there is no significant relationship concerning acetabular ante version within the two groups, although, the posterior acetabular setorial angle shows a lower median value in the osteoarthritic group

O presente estudo destinou-se a realizar uma análise comparativa entre a osteoartrite de quadris e o posicionamento acetabular através de exames radiográficos e de tomografia computadorizada. Foram incluídos 13 pacientes portadores e oito não-portadores de osteoartrite primária do quadril, recrutados no Ambulatório do Instituto de Ortopedia e Traumatologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. Os exames foram submetidos à medição das seguintes variáveis: ângulos acetabulares, ângulo centro-borda, sinal do entrecruzamento, largura e profundidade do acetábulo no RX; anteversão e ângulos setoriais acetabulares nos tomogramas. Não se verificou diferença estatisticamente significatova na anteversão acetabular entre ambos os grupos, ao passo que o ângulo acetabular setorial posterior mostrou média inferior no grupo afetado / The present study intends to develop a comparative analysis between primary hip osteoarthritis and acetabular positioning through x-ray exams and computed tomographic scans. 13 affected and 8 non-affected patients by degenerative hip disease with no underline causes are recruited within the ambulatory care service of the Institute of Orthopedics and Traumatology of the Hospital of Clinics, São Paulo University Medical School. Their radiographic exams are studied for extracting some parameters named as: acetabular angles, center edge angle, crossover sign, acetabular width and acetabular depth. Tomographic films give information to measure acetabular ante version and acetabular setorial angles. Statistically, there is no significant relationship concerning acetabular ante version within the two groups, although, the posterior acetabular setorial angle shows a lower median value in the osteoarthritic group

Background Osteoarthritis (OA) of the hip is a common disease among elderly adults and its prevalence increases with age. Hip OA is presumed to be a group of diseases resulting in the same pathological pathway, but its etiology is not completely understood. The major symptoms are joint pain, joint stiffness, impaired range of motion, and muscle weakness resulting in increased levels of physical disability (PD) and reduced quality of life. Besides the impairments of the individual subject a heavy economic burden goes along with the disease and is expected to increase due to aging societies in western countries throughout the upcoming years. Exercise therapy (ET), including elements to strengthen the hip muscles, is a common treatment in hip OA and considered to reduce pain and PD. Currently, there is only silver-level scientific evidence regarding the effectiveness of ET in hip OA due to a limited number of high quality studies. Furthermore, the optimal content and dosage, as well as the mode of delivery of ET need to be evaluated. This doctoral thesis deals with three specific aspects of hip muscle strength (HMS) in patients with hip OA: the precision of measuring HMS, training HMS, and the relevance of HMS to physical disability (PD). Three studies and one study protocol provide the scientific program of this thesis, referring to these aspects of HMS. Methods The first study (S1) investigated the reproducibility of isokinetic and isometric HMS measures in patients with hip OA. 16 subjects with unilateral or bilateral hip OA and 13 healthy subjects were tested twice, 7 days apart. A subpopulation of 11 hip OA patients was tested a third time to evaluate familiarization to these measurements. The standard error of measurement (SEM) served as the reproducibility outcome parameter. The second study (S2) investigated the feasibility of strengthening exercises and their effect on HMS in hip patients. 36 participants from an institutional training group for hip patients were allocated randomly to an intervention or control group. While the intervention group completed an eight-week progressive home-based strengthening exercise program (PHSEP) in addition to the weekly institutional supervised group-based exercise therapy (ISET), the control group continued weekly ISET, only. Exercise logs were used to monitor adherence, pain, and the applied exercise intensity of the PHSEP. Before and after the intervention period, HMS was determined using isokinetic concentric and isometric HMS measurements. Additionally, health-related quality of life was assessed by the SF36 questionnaire. These two studies served as a basis for developing strength-specific aspects of a study design for a randomized controlled trial (RCT), which was in progress at the writing of this thesis. This RCT addresses the above-mentioned lack of scientific evidence about the effectiveness of ET in hip OA. A study protocol (P1) describes this RCT, which evaluates the effectiveness of ET on pain and PD in patients with hip OA. 217 patients with hip OA were recruited from the community and allocated to one of the four groups: (1) exercise group, n = 70 (2) non-intervention group, n = 70, (3) “Sham” ultrasound group, n = 70, and (4) ultrasound group, n = 7. The main outcome measure is the change in the subscale bodily pain of the SF36. Secondary outcomes are PD assessed by the SF36 and the WOMAC questionnaire, isometric HMS, several gait variables and postural control. Finally, the relationship of HMS and PD in hip OA was investigated in a third (cross-sectional) study (S3). A stepwise regression model was applied with data from 149 subjects suffering from hip OA. The outcome variable was the self-reported physical disability, assessed with the physical function subscale of the WOMAC questionnaire. Age, gender, body mass index BMI , HMS, pain, stiffness, and range of motion were included in the statistical model as associated factors of PD. Results The results of S1 showed high variability in HMS measurements between days. The highest SEM values, indicating poorest reproducibility, were obtained for hip extension, followed by hip adduction and hip flexion measures, while the smallest values were found for hip abduction measures. Lower reproducibility occurred in patients with hip OA in comparison to healthy controls during the isometric measures of hip abduction, adduction, and flexion. Reproducibility of 11 hip OA patients was lower for the second test sequence (test-day 2 and 3) than for the first test sequence (test-day 1 and 2). The findings of S2 indicated high exercise adherence (99%) of the intervention group to the applied PHSEP. Furthermore, exercise logs reported that pain resulting from the PHSEP was low. HMS improved about 7-11% in comparison to the control group. The SF36 variables did not change throughout the exercise period. In S3, the statistical model revealed stiffness, pain, and HMS to be significant factors of self-reported physical disability in hip OA. Conclusion In conclusion, the precision of several HMS measures may be affected by hip OA and clinicians should be aware of a higher measurement error in patients with hip OA under isometric test conditions than for healthy subjects. A familiarization measurement may be an approach to diminish the measurement error. The applied PHSEP amended to an ISET is feasible for hip patients to carry out and can be applied to improve HMS. Furthermore, a significant cross-sectional relationship between HMS and PD has been evaluated, indicating that HMS may be an important factor to stimulate during exercise therapy in hip OA. The upcoming results of the RCT (P1) described in the study protocol will help to reduce the shortcomings in scientific evidence regarding the effectiveness of strengthening exercise regimes to reduce pain and PD in patients with hip OA.:List of content 1 List of figures 3 List of tables 4 List of abbreviations 5 Abstract 8 Zusammenfassung 11 Structure of the thesis 15 1 Background 16 1.1 Osteoarthritis of the hip joint 16 1.1.1 Prevalence and incidence 16 1.1.2 Etiology 17 1.1.3 Clinical symptoms and diagnosis 18 1.1.4 Socioeconomic burden 20 1.2 Hip muscle strength in osteoarthritis of the hip 23 1.2.1 Anatomical and functional aspects of the hip and its muscles 23 1.2.2 General aspects of muscle strength 25 1.2.3 Hip muscle weakness and muscle imbalances 28 1.2.4 Assessment of hip muscle strength 29 1.3 Physical disability in hip OA 35 1.3.1 General aspects of physical disability in hip OA 35 1.3.2 Assessment of physical disability in hip OA 36 1.4 Exercise therapy in hip OA 38 1.4.1 Efficacy of exercise therapy 38 1.4.2 Strengthening exercises in hip OA 39 1.5 Context of the thesis 43 1.5.1 OsteoArthritisGroup (OAG) 43 2 Scientific program - research papers 47 2.1 Research paper 1: Reproducibility of hip muscle strength measurements in hip OA 48 2.2 Research paper 2: Feasibility and efficacy of an 8-week progressive home-based strengthening exercise 58 2.3 Research paper 3: Evaluation of the therapeutic exercise regimen “Hip School": A protocol for a randomized, controlled trial 68 2.4 Research paper 4: Factors of physical disability in patients with hip osteoarthritis 81 3 Comprehensive and supplementary discussion 103 3.1 Strength measurements at the hip 103 3.1.1 Body position and fixation 103 3.1.2 Torque overshoots 104 3.1.3 Objectivity of hip muscle strength measures in osteoarthritis of the hip 104 3.1.4 Reproducibility of hip muscle strength measures in osteoarthritis of the hip 104 3.1.5 Validity of hip muscle strength measures in osteoarthritis of the hip 105 3.1.6 Isometric versus isokinetic hip muscle strength measures 106 3.2 Strengthening exercises in patients with hip OA 106 3.2.1 Feasibility and adherence to the progressive home-based strengthening exercise program 106 3.2.2 Adverse events due to the exercise intervention 107 3.2.3 Strength gains 108 3.2.4 Adaptations of the PHSEP for the RCT 109 3.3 Hip muscle strength and its relation to physical disability in patients with hip OA 110 4 Limitations 112 5 Conclusion and future perspectives 114 6 Reference list 116 7 Appendix 126 8 Affidavit 131 9 Curriculum vitae 132 / Hintergrund Coxarthrose ist eine weit verbreitete Krankheit in der älteren Bevölkerung westlicher Industrienationen. Die Bedeutung und Zahl der Neuerkrankungen nehmen mit steigendem Lebensalter zu. Schmerz, Steifheit, Bewegungseinschränkungen und Muskelschwäche zählen zu den Leitsymptomen dieser Krankheit, die sich in einer zunehmenden körperlichen Funktionseinschränkung und eingeschränkten Lebensqualität der Patienten äußern. Neben der Bedeutung für die betroffenen Patienten selbst wachsen in westlichen Industrienationen aufgrund der demographischen Entwicklung hin zu einer alternden Gesellschaft der Druck und die finanzielle Belastung auf die Renten- und Gesundheitssysteme. Die Sporttherapie wird häufig in frühen Stadien der Krankheit eingesetzt und zählt zu den konservativen Therapieverfahren. Nach aktuellem Stand der Wissenschaft scheinen sporttherapeutische Interventionen mit Trainingselementen zur Kräftigung der hüftumgebenden Muskulatur sinnvoll. Dennoch wurde die Wirksamkeit von Sporttherapie bei Coxarthrose bisher nur in einzelnen Studien nachgewiesen (Silver-level Evidence). Es fehlen qualitativ hochwertige randomisierte Kontrollgruppenstudien (RCTs). Zudem ist bislang ungeklärt, wie ein optimales Trainingsprogramm bei Coxarthrose hinsichtlich der Inhalte, Dosierung und Durchführungsmodalität zu gestalten ist, um Schmerz und körperliche Funktionseinschränkungen bestmöglich zu therapieren. Vor diesem Hintergrund beschäftigt sich die vorliegende Dissertation mit drei Aspekten der Hüftmuskelkraft bei Patienten mit Coxarthrose. Drei entsprechende Studien, die in vier wissenschaftlichen Artikeln aufgearbeitet wurden, bilden den wissenschaftlichen Schwerpunkt der Arbeit. Methode Die erste Studie (S1) befasst sich mit der Messgenauigkeit von Hüftkraftmessungen bei Coxarthrosepatienten. Unter diesem Aspekt wurden isometrische und isokinetische Kraftmessgrößen an der Hüfte bei 16 Coxarthrosepatienten und 13 gesunden Personen zwei Mal im Abstand von sieben Tagen erhoben. Bei einer Teilstichprobe von 11 Coxarthrosepatienten wurden die Messungen ein drittes Mal durchgeführt, um mögliche Gewöhnungseffekte zu evaluieren. Der Standard Error of Measurement (SEM) wurde verwendet, um den Messfehler zu quantifizieren. Die zweite Studie (S2) greift einen weiteren Aspekt auf, der sich auf das Training der Hüftmuskelkraft bei Hüftpatienten bezieht. Hier wurde die Machbarkeit eines ergänzenden Heimtrainingsprogramms zur Kräftigung der hüftumgebenden Muskulatur evaluiert sowie mögliche Auswirkungen auf die Hüftmuskelkraft untersucht. 36 Teilnehmer einer Hüftsportgruppe mit Coxarthrose und/oder einer Total-Endoprothese (TEP) wurden randomisiert in zwei Untersuchungsgruppen aufgeteilt. Während die Patienten der Kontrollgruppe im Untersuchungszeitraum weiterhin wöchentliche institutionelle sporttherapeutische Trainingseinheiten wahrnahmen, führten die Patienten der Interventionsgruppe zusätzlich Heimtrainingseinheiten zur Kräftigung der Hüftmuskeln durch. Vor und nach der Intervention wurden isometrische und isokinetische Maximalkraftmessungen durchgeführt. Die Patienten der Trainingsgruppe haben ein Trainingstagebuch geführt, um die Teilnahme am Heimtrainingsprogramm und mögliche Schwierigkeiten damit zu dokumentieren. Der SF36 Fragebogen wurde eingesetzt, um die gesundheitsbezogene Lebensqualität im Verlauf zu kontrollieren. Die Erkenntnisse der beiden beschriebenen Studien wurden verwendet, um kraftspezifische Aspekte eines Studiendesigns zu entwickeln. Dieses Studiendesign entspricht einem RCT und soll die Effektivität eines sporttherapeutischen Trainingskonzepts hinsichtlich Schmerzreduktion und Verbesserung der körperlichen Funktionsfähigkeit überprüfen. 217 Hüftarthrosepatienten werden rekrutiert und randomisiert auf eine der folgenden Untersuchungsgruppen aufgeteilt: (1) Trainingsgruppe, n = 70 (2) Kontrollgruppe ohne Intervention, n = 70, (3) “Schein” Ultraschallgruppe, n = 70, und (4) Ultraschallgruppe, n = 7. Die primäre Zielgröße ist Veränderung in der Subskala „Körperliche Schmerzen“ des SF36-Fragebogens. Sekundäre Zielgrößen sind Schmerz und Körperliche Funktionsfähigkeit aus dem WOMAC-Fragebogen, weiteren Subskalen des SF36-Fragebogens, isometrische Hüftmuskelkraft, verschiedene Variablen des Gangs und posturale Kontrolle. Die Bedeutung der Hüftmuskelkraft auf die alltagsrelevante körperliche Funktionsfähigkeit stellt den dritten Aspekt dieser Dissertation dar und wurde in Studie 3 (S3), einer Querschnittsuntersuchung an 149 Coxarthrosepatienten behandelt. Ziel der Studie war die Untersuchung des Zusammenhangs verschiedener Variablen und der alltagsbezogenen körperlichen Funktionsfähigkeit. In einem statistisches Modell wurde die Beziehung zwischen den Variablen: Hüftmuskelkraft, Body Mass Index (BMI), Alter, Geschlecht, Schmerz, Steifheit und Beweglichkeit der Hüfte und der Subskala „Körperliche Funktionsfähigkeit“ des WOMAC-Fragebogens als Maß für die alltagsbezogene körperlichen Funktionsfähigkeit berechnet. Ergebnisse In der ersten Studie (S1) wurden die größten Messfehler in den Messgrößen Hüftextension ermittelt. Danach folgten die Messgrößen Hüftadduktion und -flexion. Der geringste Messfehler wurde für Hüftabduktion ermittelt. Unter isometrischen Bedingungen wurden in den Kraftmessgrößen Hüftabduktion, -adduktion und -flexion bei Coxarthrosepatienten größere Messfehler quantifiziert als bei gesunden Personen. Zudem war die Reproduzierbarkeit in der ersten Test-Sequenz (Messtag 1 und 2) im Vergleich zur zweiten Test-Sequenz reduziert (Messtag 2 und 3). In der zweiten Studie (S2) konnte gezeigt werden, dass das verwendete Heimtrainingsprogramm sicher und selbstständig von den Hüftpatienten durchgeführt werden konnte. Die Trainingstagebücher ließen auf eine nahezu hundertprozentige Teilnahme am ergänzenden Heimtrainingsprogramm schließen und zeigten außerdem, dass das Heimtrainingsprogramm keine schmerzverursachende Wirkung hatte. Nach der Intervention war die Kraft der hüftumgebenden Muskulatur im Vergleich zur Kontrollgruppe um 7-9% gesteigert. Befunde hinsichtlich einer veränderten Lebensqualität konnten nicht registriert werden. Das statistische Modell, das in der dritten Studie (S3) eingesetzt wurde, erkannte Schmerz, Steifheit und Hüftmuskelkraft als die drei bedeutsamsten Faktoren für die alltagsbezogene körperliche Funktionsfähigkeit bei Patienten mit Coxarthrose. Schlussfolgerungen Kraftmessungen an der Hüfte scheinen erheblichen Tagesschwankungen ausgesetzt zu sein. Bei Coxarthrosepatienten und gesunden Personen scheint sich die Wiederholbarkeit von isokinetischen Kraftmessungen zu ähneln. Unter isometrischen Testbedingungen muss mit höheren Messfehlern bei Coxarthrosepatienten gerechnet und entsprechend bei der Interpretation von Ergebnissen berücksichtigt werden. Eine Gewöhnungsmessung kann den Messfehler reduzieren, birgt allerdings einen erheblich höheren finanziellen und personellen Aufwand. Das ergänzende Heimtrainingsprogramm wurde von den Patienten gut angenommen, so dass lediglich kleinere Modifikationen vorgenommen werden mussten, um es in dem geplanten RCT zu evaluieren. Zudem konnte gezeigt werden, dass die Hüftmuskelkraft zu den drei bedeutsamsten Faktoren zählt, die Einfluss auf die alltagsbezogene körperliche Funktionsfähigkeit bei Patienten mit Coxarthrose haben können. Ob diese Beziehung tatsächlich kausaler Natur ist, werden zukünftige Verlaufsstudien aufzeigen, in denen gezielt solche Faktoren der alltagsrelevanten körperliche Funktionsfähigkeit durch sporttherapeutische Maßnahmen modifiziert werden. Die ausstehenden Ergebnisse des RCT sollen die noch unzureichende wissenschaftliche Beweislage bezüglich der Wirksamkeit sporttherapeutischer Interventionen bei Coxarthrose verbessern. Dabei soll gezeigt werden, ob und in welchem Maß eine Schmerzreduktion und Verringerung der körperlichen Funktionseinschränkung erzielt werden kann.:List of content 1 List of figures 3 List of tables 4 List of abbreviations 5 Abstract 8 Zusammenfassung 11 Structure of the thesis 15 1 Background 16 1.1 Osteoarthritis of the hip joint 16 1.1.1 Prevalence and incidence 16 1.1.2 Etiology 17 1.1.3 Clinical symptoms and diagnosis 18 1.1.4 Socioeconomic burden 20 1.2 Hip muscle strength in osteoarthritis of the hip 23 1.2.1 Anatomical and functional aspects of the hip and its muscles 23 1.2.2 General aspects of muscle strength 25 1.2.3 Hip muscle weakness and muscle imbalances 28 1.2.4 Assessment of hip muscle strength 29 1.3 Physical disability in hip OA 35 1.3.1 General aspects of physical disability in hip OA 35 1.3.2 Assessment of physical disability in hip OA 36 1.4 Exercise therapy in hip OA 38 1.4.1 Efficacy of exercise therapy 38 1.4.2 Strengthening exercises in hip OA 39 1.5 Context of the thesis 43 1.5.1 OsteoArthritisGroup (OAG) 43 2 Scientific program - research papers 47 2.1 Research paper 1: Reproducibility of hip muscle strength measurements in hip OA 48 2.2 Research paper 2: Feasibility and efficacy of an 8-week progressive home-based strengthening exercise 58 2.3 Research paper 3: Evaluation of the therapeutic exercise regimen “Hip School": A protocol for a randomized, controlled trial 68 2.4 Research paper 4: Factors of physical disability in patients with hip osteoarthritis 81 3 Comprehensive and supplementary discussion 103 3.1 Strength measurements at the hip 103 3.1.1 Body position and fixation 103 3.1.2 Torque overshoots 104 3.1.3 Objectivity of hip muscle strength measures in osteoarthritis of the hip 104 3.1.4 Reproducibility of hip muscle strength measures in osteoarthritis of the hip 104 3.1.5 Validity of hip muscle strength measures in osteoarthritis of the hip 105 3.1.6 Isometric versus isokinetic hip muscle strength measures 106 3.2 Strengthening exercises in patients with hip OA 106 3.2.1 Feasibility and adherence to the progressive home-based strengthening exercise program 106 3.2.2 Adverse events due to the exercise intervention 107 3.2.3 Strength gains 108 3.2.4 Adaptations of the PHSEP for the RCT 109 3.3 Hip muscle strength and its relation to physical disability in patients with hip OA 110 4 Limitations 112 5 Conclusion and future perspectives 114 6 Reference list 116 7 Appendix 126 8 Affidavit 131 9 Curriculum vitae 132