Predicting Outcome of Total Knee Replacement Surgery in Patients With Knee Osteoarthritis

Study Overview
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Brief Summary
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Osteoarthritis (OA) is the main cause of pain and disability in elderly. For knee OA, a total knee replacement (TKR) is an effective surgical treatment, and the majority of patients report substantial pain relief and functional improvement following surgery. However, 20-40% of patients undergoing TKR are dissatisfied with postsurgical outcome. Even after revision, some patients keep complaining of persisting pain. In this study, the investigators will examine putative prognostic factors on the basis of the biopsychosocial model. Besides several psychological factors (measured with questionnaires), the investigators will assess structural impairments (such as radiographic severity of OA), functional impairments (muscle weakness and proprioceptive deficits), anesthetic procedures, immediate postoperative pain management, metabolic factors (body composition and hemoglobin A1c), inflammatory factors (C-Reactive Protein) and the investigators also will examine the role of altered central pain processing (CPP) (primary and secondary mechanical hyperalgesia, mechanical temporal summation, thermal primary and secondary hyperalgesia, endogenous pain modulation). With a longitudinal study design, this study will explore which factors are predictive of poor outcome in knee OA patients after TKR. Moreover, the interrelationship between CPP, structural, functional, metabolic, inflammatory and psychological factors, and the clinical expression of knee OA (pain, symptoms, physical performance and quality of life) will be investigated. Further research on the role of the aforementioned putative prognostic factors on postsurgical outcome could contribute to better management of these patients, since these factors may be particularly important for patient-tailored treatment.

Official Title
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Predicting Outcome of Total Knee Replacement Surgery in Patients With Knee Osteoarthritis: a Prospective Study on the Role of Altered Central Pain Processing and Structural, Functional, Metabolic, Inflammatory and Psychological Factors

Conditions
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Osteoarthritis, Knee, Arthroplasty, Replacement, Knee

Intervention / Treatment
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* Procedure: Total knee arthroplasty


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Knee OA patients >40 years awaiting TKR surgery. Both men and women of all ethnical backgrounds are included. Exclusion Criteria: Patients with diagnosis of neurological/ systemic diseases, possibly impacting pain Patients who are not capable of understanding and speaking Dutch Revision surgery

Ages Eligible for Study
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Minimum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Procedure: Total knee arthroplasty|Total knee arthroplasty surgery will be performed by different orthopedist.|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pain intensity | The subscale 'Pain' of the Knee injury and Osteoarthritis Outcome Score (KOOS) will be used as primary outcome measure. Minimum score is 0, maximum score is 36. Scores are always transformed to a 0-100 scale. The higher the score, the higher the pain intensity. | Change from baseline pain intensity at 3 months postoperative | 
| Pain intensity | The subscale 'Pain' of the Knee injury and Osteoarthritis Outcome Score (KOOS) will be used as primary outcome measure. Minimum score is 0, maximum score is 36. Scores are always transformed to a 0-100 scale. The higher the score, the higher the pain intensity. | Change from baseline pain intensity at 1 year postoperative | 
| Pain intensity | The subscale 'Pain' of the Knee injury and Osteoarthritis Outcome Score (KOOS) will be used as primary outcome measure. Minimum score is 0, maximum score is 36. Scores are always transformed to a 0-100 scale. The higher the score, the higher the pain intensity. | Change from 3 months postoperative at 1 year postoperative | 
| Pain intensity | The subscale 'Pain' of the Knee injury and Osteoarthritis Outcome Score (KOOS) will be used as primary outcome measure. Minimum score is 0, maximum score is 36. Scores are always transformed to a 0-100 scale. The higher the score, the higher the pain intensity. | Baseline (preoperative) | 
| Pain intensity | The subscale 'Pain' of the Knee injury and Osteoarthritis Outcome Score (KOOS) will be used as primary outcome measure. Minimum score is 0, maximum score is 36. Scores are always transformed to a 0-100 scale. The higher the score, the higher the pain intensity. | 3 months postoperative | 
| Pain intensity | The subscale 'Pain' of the Knee injury and Osteoarthritis Outcome Score (KOOS) will be used as primary outcome measure. Minimum score is 0, maximum score is 36. Scores are always transformed to a 0-100 scale. The higher the score, the higher the pain intensity. | 1 year postoperative | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Central pain processing: mechanical local and widespread hyperalgesia allodynia | Measured with quantitative sensory testing (QST): mechanical pain pressure threshold measured with digital algometer at the medial knee joint line, lateral knee joint line and m. Tibialis anterior of affected leg, m. extensor carpi radialis of non-dominant arm and forehead. | Change from baseline (preoperative) to 3 months postoperative | 
| Central pain processing: mechanical local and widespread hyperalgesia allodynia | Measured with quantitative sensory testing (QST): mechanical pain pressure threshold measured with digital algometer at the medial knee joint line, lateral knee joint line and m. Tibialis anterior of affected leg, m. extensor carpi radialis of non-dominant arm and forehead. | Change from baseline (preoperative) to 1 year postoperative | 
| Central pain processing: mechanical local and widespread hyperalgesia allodynia | Measured with quantitative sensory testing (QST): mechanical pain pressure threshold measured with digital algometer at the medial knee joint line, lateral knee joint line and m. Tibialis anterior of affected leg, m. extensor carpi radialis of non-dominant arm and forehead. | Change from 3 months postoperative to 1 year postoperative | 
| Central pain processing: mechanical local and widespread hyperalgesia allodynia | Measured with quantitative sensory testing (QST): mechanical pain pressure threshold measured with digital algometer at the medial knee joint line, lateral knee joint line and m. Tibialis anterior of affected leg, m. extensor carpi radialis of non-dominant arm and forehead. | Baseline (preoperative) | 
| Central pain processing: mechanical local and widespread hyperalgesia allodynia | Measured with quantitative sensory testing (QST): mechanical pain pressure threshold measured with digital algometer at the medial knee joint line, lateral knee joint line and m. Tibialis anterior of affected leg, m. extensor carpi radialis of non-dominant arm and forehead. | 3 months postoperative | 
| Central pain processing: mechanical local and widespread hyperalgesia allodynia | Measured with quantitative sensory testing (QST): mechanical pain pressure threshold measured with digital algometer at the medial knee joint line, lateral knee joint line and m. Tibialis anterior of affected leg, m. extensor carpi radialis of non-dominant arm and forehead. | 1 year postoperative | 
| Central pain processing: bottom-up sensitization | Measured with quantitative sensory testing (QST): temporal summation measured with a 60g Von Frey monofilament at the medial knee and lateral knee of affected leg, dorsal wrist of affected side | Change from baseline (preoperative) to 3 months postoperative | 
| Central pain processing: bottom-up sensitization | Measured with quantitative sensory testing (QST): temporal summation measured with a 60g Von Frey monofilament at the medial knee and lateral knee of affected leg, dorsal wrist of affected side | Change from baseline (preoperative) to 1 year postoperative | 
| Central pain processing: bottom-up sensitization | Measured with quantitative sensory testing (QST): temporal summation measured with a 60g Von Frey monofilament at the medial knee and lateral knee of affected leg, dorsal wrist of affected side | Change from 3 months postoperative to 1 year postoperative | 
| Central pain processing: bottom-up sensitization | Measured with quantitative sensory testing (QST): temporal summation measured with a 60g Von Frey monofilament at the medial knee and lateral knee of affected leg, dorsal wrist of affected side | Baseline (preoperative) | 
| Central pain processing: bottom-up sensitization | Measured with quantitative sensory testing (QST): temporal summation measured with a 60g Von Frey monofilament at the medial knee and lateral knee of affected leg, dorsal wrist of affected side | 3 months postoperative | 
| Central pain processing: bottom-up sensitization | Measured with quantitative sensory testing (QST): temporal summation measured with a 60g Von Frey monofilament at the medial knee and lateral knee of affected leg, dorsal wrist of affected side | 1 year postoperative | 
| Central pain processing: Thermal hyperalgesia | Measured with quantitative sensory testing (QST): thermal pain sensitivity measured with thermal rollers (Rolltemp II somedic senselab) at the medial knee and lateral knee of affected leg and m. extensor carpi radialis of non-dominant arm. | Change from baseline (preoperative) to 3 months postoperative | 
| Central pain processing: Thermal hyperalgesia | Measured with quantitative sensory testing (QST): thermal pain sensitivity measured with thermal rollers (Rolltemp II somedic senselab) at the medial knee and lateral knee of affected leg and m. extensor carpi radialis of non-dominant arm. | Change from baseline (preoperative) to 1 year postoperative | 
| Central pain processing: Thermal hyperalgesia | Measured with quantitative sensory testing (QST): thermal pain sensitivity measured with thermal rollers (Rolltemp II somedic senselab) at the medial knee and lateral knee of affected leg and m. extensor carpi radialis of non-dominant arm. | Change from 3 months postoperative to 1 year postoperative | 
| Central pain processing: Thermal hyperalgesia | Measured with quantitative sensory testing (QST): thermal pain sensitivity measured with thermal rollers (Rolltemp II somedic senselab) at the medial knee and lateral knee of affected leg and m. extensor carpi radialis of non-dominant arm. | Baseline (preoperative) | 
| Central pain processing: Thermal hyperalgesia | Measured with quantitative sensory testing (QST): thermal pain sensitivity measured with thermal rollers (Rolltemp II somedic senselab) at the medial knee and lateral knee of affected leg and m. extensor carpi radialis of non-dominant arm. | 3 months postoperative | 
| Central pain processing: Thermal hyperalgesia | Measured with quantitative sensory testing (QST): thermal pain sensitivity measured with thermal rollers (Rolltemp II somedic senselab) at the medial knee and lateral knee of affected leg and m. extensor carpi radialis of non-dominant arm. | 1 year postoperative | 
| Central pain processing: dysfunctional endogenous pain analgesia | Measured with quantitative sensory testing (QST): conditioned pain modulation measured Medoc at both wrists | Change from baseline (preoperative) to 3 months postoperative | 
| Central pain processing: dysfunctional endogenous pain analgesia | Measured with quantitative sensory testing (QST): conditioned pain modulation measured Medoc at both wrists | Change from baseline (preoperative) to 1 year postoperative | 
| Central pain processing: dysfunctional endogenous pain analgesia | Measured with quantitative sensory testing (QST): conditioned pain modulation measured Medoc at both wrists | Change from 3 months postoperative to 1 year postoperative | 
| Central pain processing: dysfunctional endogenous pain analgesia | Measured with quantitative sensory testing (QST): conditioned pain modulation measured Medoc at both wrists | Baseline (preoperative) | 
| Central pain processing: dysfunctional endogenous pain analgesia | Measured with quantitative sensory testing (QST): conditioned pain modulation measured Medoc at both wrists | 3 months postoperative | 
| Central pain processing: dysfunctional endogenous pain analgesia | Measured with quantitative sensory testing (QST): conditioned pain modulation measured Medoc at both wrists | 1 year postoperative | 
| Central pain processing: somatic and emotional symptoms | Questionnaire: the Central sensitization Inventory (CSI). Minimum score is 0, maximum score is 100. The higher the score, the higher the chance for the presence of central sensitization. | Change from baseline (preoperative) to 3 months postoperative | 
| Central pain processing: somatic and emotional symptoms | Questionnaire: the Central sensitization Inventory (CSI). Minimum score is 0, maximum score is 100. The higher the score, the higher the chance for the presence of central sensitization. | Change from baseline (preoperative) to 1 year postoperative | 
| Central pain processing: somatic and emotional symptoms | Questionnaire: the Central sensitization Inventory (CSI). Minimum score is 0, maximum score is 100. The higher the score, the higher the chance for the presence of central sensitization. | Change from 3 months postoperative to 1 year postoperative | 
| Central pain processing: somatic and emotional symptoms | Questionnaire: the Central sensitization Inventory (CSI). Minimum score is 0, maximum score is 100. The higher the score, the higher the chance for the presence of central sensitization. | Baseline (preoperative) | 
| Central pain processing: somatic and emotional symptoms | Questionnaire: the Central sensitization Inventory (CSI). Minimum score is 0, maximum score is 100. The higher the score, the higher the chance for the presence of central sensitization. | 3 months postoperative | 
| Central pain processing: somatic and emotional symptoms | Questionnaire: the Central sensitization Inventory (CSI). Minimum score is 0, maximum score is 100. The higher the score, the higher the chance for the presence of central sensitization. | 1 year postoperative | 
| Central pain processing: areas of pain | Body chart: Expanded distribution of Pain (EDP). The more pain locations, the more chance for the presence of central sensitization | Change from baseline (preoperative) to 3 months postoperative | 
| Central pain processing: areas of pain | Body chart: Expanded distribution of Pain (EDP). The more pain locations, the more chance for the presence of central sensitization | Change from baseline (preoperative) to 1 year postoperative | 
| Central pain processing: areas of pain | Body chart: Expanded distribution of Pain (EDP). The more pain locations, the more chance for the presence of central sensitization | Change from 3 months postoperative to 1 year postoperative | 
| Central pain processing: areas of pain | Body chart: Expanded distribution of Pain (EDP). The more pain locations, the more chance for the presence of central sensitization | Baseline (preoperative) | 
| Central pain processing: areas of pain | Body chart: Expanded distribution of Pain (EDP). The more pain locations, the more chance for the presence of central sensitization | 3 months postoperative | 
| Central pain processing: areas of pain | Body chart: Expanded distribution of Pain (EDP). The more pain locations, the more chance for the presence of central sensitization | 1 year postoperative | 
| Psychosocial factors: pain catastrophizing | Measured with Pain Catastrophizing Scale (PCS). Minimum score is 0, maximum score is 52. The higher the score, the higher the pain catastrophizing. | Change from baseline (preoperative) to 3 months postoperative | 
| Psychosocial factors: pain catastrophizing | Measured with Pain Catastrophizing Scale (PCS). Minimum score is 0, maximum score is 52. The higher the score, the higher the pain catastrophizing. | Change from baseline (preoperative) to 1 year postoperative | 
| Psychosocial factors: pain catastrophizing | Measured with Pain Catastrophizing Scale (PCS). Minimum score is 0, maximum score is 52. The higher the score, the higher the pain catastrophizing. | Change from 3 months postoperative to 1 year postoperative | 
| Psychosocial factors: pain catastrophizing | Measured with Pain Catastrophizing Scale (PCS). Minimum score is 0, maximum score is 52. The higher the score, the higher the pain catastrophizing. | Baseline (preoperative) | 
| Psychosocial factors: pain catastrophizing | Measured with Pain Catastrophizing Scale (PCS). Minimum score is 0, maximum score is 52. The higher the score, the higher the pain catastrophizing. | 3 months postoperative | 
| Psychosocial factors: pain catastrophizing | Measured with Pain Catastrophizing Scale (PCS). Minimum score is 0, maximum score is 52. The higher the score, the higher the pain catastrophizing. | 1 year postoperative | 
| Psychosocial factors: illness perceptions | Illness perception questionnaire-revised (IPQ-R) Identity dimension: yes = 1; no = 0 min score= 0, max score= 18 Other dimensions: min score= 38, max score= 190 strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 Causal dimension: strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 min score= 18, max score= 90 High scores on the identity, timeline, consequences, and cyclical dimensions represent strongly held beliefs about the number of symptoms attributed to the illness, the chronicity of the condition, the negative consequences of the illness, and the cyclical nature of the condition. High scores on the personal control, treatment control and coherence dimensions, represent positive beliefs about the controllability of the illness and a personal understanding of the condition. | Change from baseline (preoperative) to 3 months postoperative | 
| Psychosocial factors: illness perceptions | Illness perception questionnaire-revised (IPQ-R) Identity dimension: yes = 1; no = 0 min score= 0, max score= 18 Other dimensions: min score= 38, max score= 190 strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 Causal dimension: strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 min score= 18, max score= 90 High scores on the identity, timeline, consequences, and cyclical dimensions represent strongly held beliefs about the number of symptoms attributed to the illness, the chronicity of the condition, the negative consequences of the illness, and the cyclical nature of the condition. High scores on the personal control, treatment control and coherence dimensions, represent positive beliefs about the controllability of the illness and a personal understanding of the condition. | Change from baseline (preoperative) to 1 year postoperative | 
| Psychosocial factors: illness perceptions | Illness perception questionnaire-revised (IPQ-R) Identity dimension: yes = 1; no = 0 min score= 0, max score= 18 Other dimensions: min score= 38, max score= 190 strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 Causal dimension: strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 min score= 18, max score= 90 High scores on the identity, timeline, consequences, and cyclical dimensions represent strongly held beliefs about the number of symptoms attributed to the illness, the chronicity of the condition, the negative consequences of the illness, and the cyclical nature of the condition. High scores on the personal control, treatment control and coherence dimensions, represent positive beliefs about the controllability of the illness and a personal understanding of the condition. | Change from 3 months postoperative to 1 year postoperative | 
| Psychosocial factors: illness perceptions | Illness perception questionnaire-revised (IPQ-R) Identity dimension: yes = 1; no = 0 min score= 0, max score= 18 Other dimensions: min score= 38, max score= 190 strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 Causal dimension: strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 min score= 18, max score= 90 High scores on the identity, timeline, consequences, and cyclical dimensions represent strongly held beliefs about the number of symptoms attributed to the illness, the chronicity of the condition, the negative consequences of the illness, and the cyclical nature of the condition. High scores on the personal control, treatment control and coherence dimensions, represent positive beliefs about the controllability of the illness and a personal understanding of the condition. | Baseline (preoperative) | 
| Psychosocial factors: illness perceptions | Illness perception questionnaire-revised (IPQ-R) Identity dimension: yes = 1; no = 0 min score= 0, max score= 18 Other dimensions: min score= 38, max score= 190 strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 Causal dimension: strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 min score= 18, max score= 90 High scores on the identity, timeline, consequences, and cyclical dimensions represent strongly held beliefs about the number of symptoms attributed to the illness, the chronicity of the condition, the negative consequences of the illness, and the cyclical nature of the condition. High scores on the personal control, treatment control and coherence dimensions, represent positive beliefs about the controllability of the illness and a personal understanding of the condition. | 3 months postoperative | 
| Psychosocial factors: illness perceptions | Illness perception questionnaire-revised (IPQ-R) Identity dimension: yes = 1; no = 0 min score= 0, max score= 18 Other dimensions: min score= 38, max score= 190 strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 Causal dimension: strongly disagree =1, disagree =2, neither agree or disagree = 3, agree = 4, strongly agree = 5 min score= 18, max score= 90 High scores on the identity, timeline, consequences, and cyclical dimensions represent strongly held beliefs about the number of symptoms attributed to the illness, the chronicity of the condition, the negative consequences of the illness, and the cyclical nature of the condition. High scores on the personal control, treatment control and coherence dimensions, represent positive beliefs about the controllability of the illness and a personal understanding of the condition. | 1 year postoperative | 
| Psychosocial factors: anxiety | Measured with Hospital Anxiety and Depression Scale (HADS), subscale anxiety. Minimum score is 0, maximum score is 21. The higher the score, the higher the anxiety. | Change from baseline (preoperative) to 3 months postoperative | 
| Psychosocial factors: anxiety | Measured with Hospital Anxiety and Depression Scale (HADS), subscale anxiety. Minimum score is 0, maximum score is 21. The higher the score, the higher the anxiety. | Change from baseline (preoperative) to 1 year postoperative | 
| Psychosocial factors: anxiety | Measured with Hospital Anxiety and Depression Scale (HADS), subscale anxiety. Minimum score is 0, maximum score is 21. The higher the score, the higher the anxiety. | Change from 3 months postoperative to 1 year postoperative | 
| Psychosocial factors: anxiety | Measured with Hospital Anxiety and Depression Scale (HADS), subscale anxiety. Minimum score is 0, maximum score is 21. The higher the score, the higher the anxiety. | Baseline (preoperative) | 
| Psychosocial factors: anxiety | Measured with Hospital Anxiety and Depression Scale (HADS), subscale anxiety. Minimum score is 0, maximum score is 21. The higher the score, the higher the anxiety. | 3 months postoperative | 
| Psychosocial factors: anxiety | Measured with Hospital Anxiety and Depression Scale (HADS), subscale anxiety. Minimum score is 0, maximum score is 21. The higher the score, the higher the anxiety. | 1 year postoperative | 
| Psychosocial factors: depression | Measured with Hospital Anxiety and Depression Scale (HADS), subscale depression. Minimum score is 0, maximum score is 21. The higher the score, the higher the depression. | Change from baseline (preoperative) to 3 months postoperative | 
| Psychosocial factors: depression | Measured with Hospital Anxiety and Depression Scale (HADS), subscale depression. Minimum score is 0, maximum score is 21. The higher the score, the higher the depression. | Change from baseline (preoperative) to 1 year postoperative | 
| Psychosocial factors: depression | Measured with Hospital Anxiety and Depression Scale (HADS), subscale depression. Minimum score is 0, maximum score is 21. The higher the score, the higher the depression. | Change from 3 months postoperative to 1 year postoperative | 
| Psychosocial factors: depression | Measured with Hospital Anxiety and Depression Scale (HADS), subscale depression. Minimum score is 0, maximum score is 21. The higher the score, the higher the depression. | Baseline (preoperative) | 
| Psychosocial factors: depression | Measured with Hospital Anxiety and Depression Scale (HADS), subscale depression. Minimum score is 0, maximum score is 21. The higher the score, the higher the depression. | 3 months postoperative | 
| Psychosocial factors: depression | Measured with Hospital Anxiety and Depression Scale (HADS), subscale depression. Minimum score is 0, maximum score is 21. The higher the score, the higher the depression. | 1 year postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Hamstrings | Strength m. Hamstrings of both legs, measured with Biodex System 4 pro - dynamometer | Change from baseline (preoperative) to 3 months postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Hamstrings | Strength m. Hamstrings of both legs, measured with Biodex System 4 pro - dynamometer | Change from baseline (preoperative) to 1 year postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Hamstrings | Strength m. Hamstrings of both legs, measured with Biodex System 4 pro - dynamometer | Change from 3 months postoperative to 1 year postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Hamstrings | Strength m. Hamstrings of both legs, measured with Biodex System 4 pro - dynamometer | 3 months postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Hamstrings | Strength m. Hamstrings of both legs, measured with Biodex System 4 pro - dynamometer | Baseline (preoperative) | 
| Functional factors: Maximal voluntary muscle strength m. Hamstrings | Strength m. Hamstrings of both legs, measured with Biodex System 4 pro - dynamometer | 1 year postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Quadriceps | Strength m. Quadriceps of both legs, measured with Biodex System 4 pro - dynamometer | Change from baseline (preoperative) to 3 months postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Quadriceps | Strength m. Quadriceps of both legs, measured with Biodex System 4 pro - dynamometer | Change from baseline (preoperative) to 1 year postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Quadriceps | Strength m. Quadriceps of both legs, measured with Biodex System 4 pro - dynamometer | Change from 3 months postoperative to 1 year postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Quadriceps | Strength m. Quadriceps of both legs, measured with Biodex System 4 pro - dynamometer | Baseline (preoperative) | 
| Functional factors: Maximal voluntary muscle strength m. Quadriceps | Strength m. Quadriceps of both legs, measured with Biodex System 4 pro - dynamometer | 3 months postoperative | 
| Functional factors: Maximal voluntary muscle strength m. Quadriceps | Strength m. Quadriceps of both legs, measured with Biodex System 4 pro - dynamometer | 1 year postoperative | 
| Functional factors: proprioceptive accuracy | Proprioception of the knee of both legs, measured with inclinometer | Change from baseline (preoperative) to 3 months postoperative | 
| Functional factors: proprioceptive accuracy | Proprioception of the knee of both legs, measured with inclinometer | Change from baseline (preoperative) to 1 year postoperative | 
| Functional factors: proprioceptive accuracy | Proprioception of the knee of both legs, measured with inclinometer | Change from 3 months postoperative to 1 year postoperative | 
| Functional factors: proprioceptive accuracy | Proprioception of the knee of both legs, measured with inclinometer | Baseline (preoperative) | 
| Functional factors: proprioceptive accuracy | Proprioception of the knee of both legs, measured with inclinometer | 3 months postoperative | 
| Functional factors: proprioceptive accuracy | Proprioception of the knee of both legs, measured with inclinometer | 1 year postoperative | 
| Functional factors: leg strength and endurance | Measured with 30 seconds Timed Chair-Stand-Test | Change from baseline (preoperative) to 3 months postoperative | 
| Functional factors: leg strength and endurance | Measured with 30 seconds Timed Chair-Stand-Test | Change from baseline (preoperative) to 1 year postoperative | 
| Functional factors: leg strength and endurance | Measured with 30 seconds Timed Chair-Stand-Test | Change from 3 months postoperative to 1 year postoperative | 
| Functional factors: leg strength and endurance | Measured with 30 seconds Timed Chair-Stand-Test | Baseline (preoperative) | 
| Functional factors: leg strength and endurance | Measured with 30 seconds Timed Chair-Stand-Test | 3 months postoperative | 
| Functional factors: leg strength and endurance | Measured with 30 seconds Timed Chair-Stand-Test | 1 year postoperative | 
| Patient demographics | measured with Knee Society Scoring System (KSS): subscale patient demographics (nominal) | Baseline (preoperative) | 
| Alignment | measured with Knee Society Scoring System (KSS): subscale objective knee score 'alignment': weight-bearing anterior-posterior radiograph measuring the femoral-tibial (Anatomic) axis. Minimum is 0, maximum is 25. The higher the score, the better the alignment. | Baseline (preoperative) | 
| Instability | measured with Knee Society Scoring System (KSS): subscale objective knee score 'instability'. Minimum is 0, maximum is 25. The higher the score, the better the stability. | Baseline (preoperative) | 
| Joint motion | measured with Knee Society Scoring System (KSS): subscale objective knee score 'joint motion'. Minimum is 0, maximum can be higher than 25. One point for every joint motion of 5 degrees. The higher the score, the better the joint motion. | Baseline (preoperative) | 
| Pain symptoms | measured with Knee Society Scoring System (KSS): subscale symptoms. Minimum score is 0, maximum score is 25. The higher the score, the worse the pain symptoms. | Change from baseline (preoperative) to 3 months postoperative | 
| Pain symptoms | measured with Knee Society Scoring System (KSS): subscale symptoms. Minimum score is 0, maximum score is 25. The higher the score, the worse the pain symptoms. | Change from baseline (preoperative) to 1 year postoperative | 
| Pain symptoms | measured with Knee Society Scoring System (KSS): subscale symptoms. Minimum score is 0, maximum score is 25. The higher the score, the worse the pain symptoms. | Change from 3 months postoperative to 1 year postoperative | 
| Pain symptoms | measured with Knee Society Scoring System (KSS): subscale symptoms. Minimum score is 0, maximum score is 25. The higher the score, the worse the pain symptoms. | Baseline (preoperative) | 
| Pain symptoms | measured with Knee Society Scoring System (KSS): subscale symptoms. Minimum score is 0, maximum score is 25. The higher the score, the worse the pain symptoms. | 3 months postoperative | 
| Pain symptoms | measured with Knee Society Scoring System (KSS): subscale symptoms. Minimum score is 0, maximum score is 25. The higher the score, the worse the pain symptoms. | 1 year postoperative | 
| Patient expectations | measured with Knee Society Scoring System (KSS): subscale patient expectations. Minimum score is 0, maximum score is 15. The higher the score, the higher the patient's opinion on the extent to which the patient expects that the operation will improve their knee pain, and their ability to perform their activities of daily living and recreational activities | Baseline (preoperative) | 
| Patient expectations fulfillment | measured with Knee Society Scoring System (KSS): subscale patient expectations. Minimum score is 0, maximum score is 15. The higher the score, the higher the patient's opinion on the extent to which the outcome after the operation has met the patient's pre-operative expectations with respect to pain and function | 3 months postoperative | 
| Patient expectations fulfillment | measured with Knee Society Scoring System (KSS): subscale patient expectations. Minimum score is 0, maximum score is 15. The higher the score, the higher the patient's opinion on the extent to which the outcome after the operation has met the patient's pre-operative expectations with respect to pain and function | 1 year postoperative | 
| Patient expectations fulfillment | measured with Knee Society Scoring System (KSS): subscale patient expectations. Minimum score is 0, maximum score is 15. The higher the score, the higher the patient's opinion on the extent to which the outcome after the operation has met the patient's pre-operative expectations with respect to pain and function | Change from 3 months postoperative to 1 year postoperative | 
| Patient satisfaction | measured with Knee Society Scoring System (KSS): subscale patient satisfaction. Minimum score is 0, maximum score is 40. The higher the score, the more satisfied the patient feels with their knee. | Change from baseline (preoperative) to 3 months postoperative | 
| Patient satisfaction | measured with Knee Society Scoring System (KSS): subscale patient satisfaction. Minimum score is 0, maximum score is 40. The higher the score, the more satisfied the patient feels with their knee. | Change from baseline (preoperative) to 1 year postoperative | 
| Patient satisfaction | measured with Knee Society Scoring System (KSS): subscale patient satisfaction. Minimum score is 0, maximum score is 40. The higher the score, the more satisfied the patient feels with their knee. | Change from 3 months postoperative to 1 year postoperative | 
| Patient satisfaction | measured with Knee Society Scoring System (KSS): subscale patient satisfaction. Minimum score is 0, maximum score is 40. The higher the score, the more satisfied the patient feels with their knee. | Baseline (preoperative) | 
| Patient satisfaction | measured with Knee Society Scoring System (KSS): subscale patient satisfaction. Minimum score is 0, maximum score is 40. The higher the score, the more satisfied the patient feels with their knee. | 3 months postoperative | 
| Patient satisfaction | measured with Knee Society Scoring System (KSS): subscale patient satisfaction. Minimum score is 0, maximum score is 40. The higher the score, the more satisfied the patient feels with their knee. | 1 year postoperative | 
| Functional score | measured with Knee Society Scoring System (KSS): subscale functional score. Minimum score is 0, maximum score is 100. The higher the score, the better the functionality of the patient | Change from baseline (preoperative) to 3 months postoperative | 
| Functional score | measured with Knee Society Scoring System (KSS): subscale functional score. Minimum score is 0, maximum score is 100. The higher the score, the better the functionality of the patient | Change from baseline (preoperative) to 1 year postoperative | 
| Functional score | measured with Knee Society Scoring System (KSS): subscale functional score. Minimum score is 0, maximum score is 100. The higher the score, the better the functionality of the patient | Change from 3 months postoperative to 1 year postoperative | 
| Functional score | measured with Knee Society Scoring System (KSS): subscale functional score. Minimum score is 0, maximum score is 100. The higher the score, the better the functionality of the patient | Baseline (preoperative) | 
| Functional score | measured with Knee Society Scoring System (KSS): subscale functional score. Minimum score is 0, maximum score is 100. The higher the score, the better the functionality of the patient | 3 months postoperative | 
| Functional score | measured with Knee Society Scoring System (KSS): subscale functional score. Minimum score is 0, maximum score is 100. The higher the score, the better the functionality of the patient | 1 year postoperative | 
| Metabolic factors: Fat mass | Measured with Bio-electrical Impedance Analyses (BIA) | Change from baseline (preoperative) to 3 months postoperative | 
| Metabolic factors: Fat mass | Measured with Bio-electrical Impedance Analyses (BIA) | Change from baseline (preoperative) to 1 year postoperative | 
| Metabolic factors: Fat mass | Measured with Bio-electrical Impedance Analyses (BIA) | Change from 3 months postoperative to 1 year postoperative | 
| Metabolic factors: Fat mass | Measured with Bio-electrical Impedance Analyses (BIA) | Baseline (preoperative) | 
| Metabolic factors: Fat mass | Measured with Bio-electrical Impedance Analyses (BIA) | 3 months postoperative | 
| Metabolic factors: Fat mass | Measured with Bio-electrical Impedance Analyses (BIA) | 1 year postoperative | 
| Metabolic factors: Lean mass | Measured with Bio-electrical Impedance Analyses (BIA) | Change from baseline (preoperative) to 3 months postoperative | 
| Metabolic factors: Lean mass | Measured with Bio-electrical Impedance Analyses (BIA) | Change from baseline (preoperative) to 1 year postoperative | 
| Metabolic factors: Lean mass | Measured with Bio-electrical Impedance Analyses (BIA) | Change from 3 months postoperative to 1 year postoperative | 
| Metabolic factors: Lean mass | Measured with Bio-electrical Impedance Analyses (BIA) | Baseline (preoperative) | 
| Metabolic factors: Lean mass | Measured with Bio-electrical Impedance Analyses (BIA) | 3 months postoperative | 
| Metabolic factors: Lean mass | Measured with Bio-electrical Impedance Analyses (BIA) | 1 year postoperative | 
| Metabolic factors: Body mass index (BMI) | Measured with length of patient (cm) and weight of patient (kg) | Change from baseline (preoperative) to 3 months postoperative | 
| Metabolic factors: Body mass index (BMI) | Measured with length of patient (cm) and weight of patient (kg) | Change from baseline (preoperative) to 1 year postoperative | 
| Metabolic factors: Body mass index (BMI) | Measured with length of patient (cm) and weight of patient (kg) | Change from 3 months postoperative to 1 year postoperative | 
| Metabolic factors: Body mass index (BMI) | Measured with length of patient (cm) and weight of patient (kg) | Baseline (preoperative) | 
| Metabolic factors: Body mass index (BMI) | Measured with length of patient (cm) and weight of patient (kg) | 3 months postoperative | 
| Metabolic factors: Body mass index (BMI) | Measured with length of patient (cm) and weight of patient (kg) | 1 year postoperative | 
| Metabolic factors: body composition | Measured with Bioelectrical Impedance Analysis (BIA) | Baseline (preoperative), 3 months postoperative, 1 year postoperative. | 
| Metabolic factors: venous blood sample | Measured with A1C test or glycohemoglobin test | Change from baseline (preoperative) to 3 months postoperative | 
| Metabolic factors: venous blood sample | Measured with A1C test or glycohemoglobin test | Change from baseline (preoperative) to 1 year postoperative | 
| Metabolic factors: venous blood sample | Measured with A1C test or glycohemoglobin test | Change from 3 months postoperative to 1 year postoperative | 
| Metabolic factors: venous blood sample | Measured with A1C test or glycohemoglobin test | Baseline (preoperative) | 
| Metabolic factors: venous blood sample | Measured with A1C test or glycohemoglobin test | 3 months postoperative | 
| Metabolic factors: venous blood sample | Measured with A1C test or glycohemoglobin test | 1 year postoperative. | 
| Structural factors | Measured with Kellgren and Lawrence scale on radiography | Baseline (preoperative) | 
| Inflammatory factors: signs of inflammation | Measured with the C-reactive protein levels in blood sample (collected from patient record) | Baseline (preoperative) | 
| Anesthetic procedure | General anesthesia, spinal anesthesia or combination with peripheral block | During surgery | 
| Clinical pain score | Measured with numeric rating pain scale | day 1 and 2 postoperative |