Abstract
Osteoarthritis (OA) is one of the 10 most disabling diseases in developed countries and worldwide estimates are that 10% of men and 18% of women aged over 60 years have symptomatic OA, including moderate and severe forms. Total joint replacement (TJR) is considered the most effective treatment for end-stage OA in those who have exhausted available conservative interventions. The demand for TJR is continually rising due to the ageing population; in the United States, more than 1 million TJRs were performed in 2010 and the number of procedures is projected to exceed 4 million in the US by 2030. It has been estimated that of all hip and knee replacements performed, approximately one quarter of the patients may be considered inappropriate candidates. Predicting who will benefit from TJR and who will not would seem critical in terms of containing the current and projected expenditure as well as improving satisfaction in TJR recipients. Few formal predictive tools are available to aid referring clinicians to determine those likely to be good or poor responders to surgery and current available tools tend to focus on disease severity alone with little consideration of risk factors that may predict a poor outcome or impede an effective response to surgery. This review examines the tools available to assist with assessing appropriateness for TJR; investigates the modifiable risk factors associated with poor outcome; and identifies areas for future research in selecting those appropriate for joint replacement.
Background
Osteoarthritis (OA) is one of the 10 most disabling diseases in developed countries and worldwide estimates are that 10% of men and 18% of women aged over 60 years have symptomatic OA, including moderate and severe forms . Globally, musculoskeletal (MSK) disorders are the second largest contributor to years lived with disability, with OA of the hips and knees combined being the third most prevalent MSK disorder . Age is the strongest predictor of the development and progression of OA, and as such the number of people suffering with OA is expected to increase over the coming years due to the ageing of the population .
Based on best available evidence, the American College of Rheumatology (ACR) strongly recommends aquatic and aerobic and/or land-based resistance exercise as first-line interventions for individuals with hip or knee OA . Weight loss in those who are overweight is also strongly recommended. Pharmacological interventions are conditionally recommended and include: paracetamol, nonsteroidal anti-inflammatory drugs (NSAIDs), tramadol and intra-articular corticosteroid injections . However, for those who have exhausted available conservative interventions, total joint replacement (TJR) is considered the most effective treatment for end-stage OA .
The demand for TJR is continually rising due to the ageing population and between 2000 and 2009, the average rate of hip replacement increased by more than 25% and by nearly 100% for knee replacement . In the United States, more than 1 million hip and knee replacements were performed in 2010 at an average per case cost of US $17,000 and $15,000, respectively , with an estimated total financial outlay for TJR procedures in this one year alone at $16.5 billion dollars in health-care costs. With the number of procedures projected to exceed 4 million in the US by 2030 and many other Organisation for Economic Co-operation and Development (OECD) countries demonstrating similar increasing trajectories for hip and knee replacement , preparing to meet this challenge will be a major priority for health services globally.
TJR improves quality of life by reducing pain, joint deformity and loss of function . It is regarded as a successful procedure with a revision rate of only 0.5% per annum from index surgery . However, revision surgery alone as a sole index of failure has been called into question because of the potential for underestimating the problem . There is a significant proportion (20–40%) of patients who endure years of dissatisfaction and disability despite procedures appearing technically and radiologically satisfactory . Many of these patients do not undergo revision surgery, but all add to the community’s burden of health care as clinicians and allied services strive to remedy their dissatisfaction.
It has been estimated that of all hip and knee replacements performed, approximately one quarter may be considered inappropriate candidates when assessed against a validated pain and functional threshold above which surgery would be indicated to achieve a clinically relevant improvement . Predicting who will benefit from TJR and who will not would seem critical in terms of containing the current and projected expenditure as well as the level of dissatisfaction expressed by a significant proportion of TJR recipients. It would seem reasonable that clinicians and hospital management adopt criteria for both selecting candidates and for assessing appropriateness for surgery. Yet there are currently very few formal predictive tools available to aid referring clinicians to determine those likely to be good or poor responders to surgery.
Determining appropriateness for surgery should not be based on disease severity alone but also take into account an individual’s capacity to benefit from TJR . The decision to refer for surgery, should be based on a number of key considerations: i) When measured against validated criteria, does the individual’s objective (radiographic) and subjective (clinical) presentation warrant specialist referral, ii) To what extent have effective conservative treatments have been trialled, iii) To what extent is an individual’s risk factors likely to impede their capacity to benefit from surgery and iv) What strategies can be applied prior to specialist referral to mitigate the risk in those individuals identified as likely to be poor responders to surgery. However, current available tools to guide specialist referral tend to focus on disease severity alone with little consideration of risk factors that may predict a poor outcome or impede an effective response to surgery.
This review examines the tools available to assist with assessing appropriateness for TJR; investigates the modifiable risk factors associated with poor outcome; and identifies areas for future research in selecting those appropriate for joint replacement.
Selecting TJR candidates based on disease severity
It is generally recommended that patients with severe symptomatic OA, who have pain that has failed to respond to conservative treatments and who have progressive limitation in activities of daily living should be referred to an orthopaedic surgeon for evaluation . However, opinions about the indications for TJR based on the severity of joint disease and symptomatology vary greatly between referring physicians and surgeons . While there are no universally accepted criteria to determine the indications for TJR, there are algorithms that have been developed to assist with determining appropriateness of surgery based on clinical presentation. Although these algorithms may be used to aid the decision to refer for specialist evaluation, they fail to take into account individual risk factors which may impact on patient outcomes after TJR and few of these algorithms have undergone rigorous evaluation .
Algorithms based on appropriateness criteria
The most widely validated algorithms are those that have used the RAND/UCLA appropriateness method (RAM) , which combines expert opinion with available scientific evidence to create explicit criteria for the appropriateness of a medical or surgical intervention . Quintana et al. and Escobar et al. have developed explicit criteria for hip and knee replacement, respectively, based on this method. Appropriateness is defined as meaning that the expected health benefit exceeds the expected negative consequences by a sufficiently wide margin to make a treatment worth performing .
Quintana et al. developed explicit criteria for appropriateness in total hip replacement (THR) based on a comprehensive list of indications for THR which were initially derived from an extensive literature review . Individual patient variables included: age, bone quality, surgical risk, prior non-surgical procedures performed and pain and functional limitation with each variable categorised based on accepted classification systems published in the literature. All possible combinations of these variables and categories ( n = 216) were reviewed by expert panels who rated appropriateness for surgery for each of the 216 indications using a modified Delphi process. Each scenario was rated as appropriate, uncertain or inappropriate.
To determine the validity of the panel’s findings, a random cohort of patients undergoing THR completed the Western Ontario and McMaster Universities Arthritis Index (WOMAC) , a disease-specific questionnaire, and the SF-36 , a generic health questionnaire, prior to and 3 months after surgery. Patients were classified into one of the three appropriateness groups (appropriate, uncertain and inappropriate) and the improvement in health scores was assessed for each group. Significantly greater improvements in scores were demonstrated for those who were considered appropriate for surgery compared to those considered inappropriate and the differences were clinically meaningful.
Quintana’s appropriateness criteria are expressed as a regression tree which outlines six broad scenarios where referral for consideration for THR would be deemed appropriate ( Table 1 ). For a complete view of the decision tree including appropriate, uncertain and inappropriate scenarios, see Quintana et al. . The evaluation of appropriateness for THR is initially based on the degree of pain on presentation. Where pain is severe and prior conservative measures have been undertaken correctly, THR is deemed appropriate in those with functional limitation, whether minor moderate or severe. In cases where a conservative treatment path has not been followed correctly, surgery is only deemed appropriate in those with severe functional limitation. In those whom pain is mild to moderate and prior conservative treatments have been undertaken correctly, surgery is deemed appropriate for those with severe functional limitation and low surgical risk.
| Pain a | Prior conservative treatment undertaken a | Functional Limitation a | American Society of Anaesthesiologist (ASA) Score a |
|---|---|---|---|
| Mild | Correctly | Severe | 1–3 |
| Moderate | Correctly | Severe | 1–3 |
| Severe | Correctly | Minor | Not required |
| Severe | Correctly | Moderate | Not required |
| Severe | Correctly | Severe | Not required |
| Severe | Incorrectly | Severe | Not required |
a For classification definitions of variables in the algorithm, see appendix in Quintana et al. .
Using a similar process, Escobar et al. have used the RAND method to develop explicit criteria for appropriateness in total knee replacement (TKR), with a few notable differences; radiographic assessment is included in the TKR algorithm and the analyses exclude those who have undergone prior surgical management, arthroscopy and/or tibial osteotomy . Initially, there were 864 indications for TKR identified through a literature review which was reduced to 624 as a result of modifying the variables included and finally 156 of the most frequent scenarios were reviewed by an expert panel for appropriateness assessment. For a complete view of the decision tree including appropriate, uncertain and inappropriate scenarios, see Escobar et al. .
For TKR, surgery was only determined to be appropriate in those with intense to severe pain using a defined set of criteria ( Table 2 ). In those with severe pain and Ahlback classification of I, surgery was deemed appropriate in those who were aged 66 years or older with limited mobility. In those with both intense or severe pain and Ahlback classification of II–III, surgery was deemed appropriate in those aged 55 years or older with limited mobility, whereas in those with Ahlback classification of IV–V, surgery was deemed appropriate in those aged 55 years or older irrespective of mobility. In those younger than 55 years of age with Ahlback classification of IV–V, surgery was only deemed appropriate in those with bicompartmental involvement (including the patella–femoral joint) or tricompartmental OA and again this was irrespective of mobility status.
| Pain a | Ahlback a | Age a | Mobility a | Compartmental involvement a |
|---|---|---|---|---|
| Severe | I | >65 years | Limited | Not required |
| Intense–severe | II–III | ≥55 years | Limited | Not required |
| Intense–severe | IV–V | ≥55 years | Not required | Not required |
| Intense–severe | IV–V | <55 years | Not required | Bicompartmental |
| Intense–severe | IV–V | <55 years | Not required | Tricompartmental |
a For classification definitions of variables in the algorithm, refer Escobar et al. .
While the above algorithms have undergone a validation process , several limitations diminish their usefulness as a clinical guide for specialist referral and these warrant mentioning. The THR algorithm does not take into account radiographic severity, which has, in recent literature, been revealed as an important predictor of the THR outcome in the short and longer term . The use of the American Society of Anaesthesiologist (ASA) score designed for anaesthesiologists to classify surgical risk may restrict the tool’s usefulness in the primary care setting. The algorithm for TKR excludes those who have undergone prior surgical management, diminishing its broad applicability to the population who present with late-stage knee OA, given that arthroscopy is common in the preceding 1–2 years amongst those presenting for TKR .
The most notable limitation with these tools, however, is acknowledged by the authors and, that is, a significant proportion of scenarios are classified by the expert panel as ‘uncertain’ in terms of appropriateness for TJR and for the uncertain group, there were similar improvements in health status and symptom relief as for the group deemed appropriate candidates for surgery . This suggests that a decision to refer for orthopaedic consultation based solely on the appropriateness algorithm would disadvantage a substantial proportion of individuals who may otherwise derive benefit from TJR.
Algorithms based on prioritisation
The Multi-attribute Arthritis Prioritisation Tool (MAPT) score is used as a tool to prioritise the management and care of patients with OA of the hip or knee waiting for primary THR or TKR surgery . The MAPT consists of a series of 11 questions that are answered by the patient. It aims to assess the severity of pain, functional disability, psychological health, economic impact and deterioration in those with hip or knee symptoms. Higher MAPT scores suggest higher perceived disability and pain by the patient and should trigger earlier referral to a specialist clinic or prioritisation for surgery . MAPT can be used to facilitate fast-tracking of patients with the greatest need for TJR, monitoring for deterioration in those waiting for surgery or having a trial of non-operative treatment and deferment of surgery for those who may benefit from further non-operative treatments .
The MAPT is routinely administered in hospitals across Victoria, Australia, but there is a lack of evidence that the prioritisation for TJR surgery according to MAPT scores correlates with response to surgery. One study of patients on the waiting list for TJR demonstrated that there is no correlation between MAPT scores and radiographic severity of arthritis. David et al. found that the mean MAPT score was higher (80.76) in patients with a lower Kellgren–Lawrence (KL) radiographic grade of arthritis (grade 1 or 2) than the mean MAPT score (60.17) in patients with a higher radiographic grade of arthritis (grade 3 or 4). A MAPT score of 21–60 is considered middle priority, whereas a score >60 is considered highest priority indicating that surgery is warranted in the immediate term . These findings suggest that using the MAPT score to aid the decision for specialist referral or to prioritise for surgery without consideration of radiographic severity may lead to TJR surgery being undertaken in individuals with early OA where conservative treatment is warranted.
The Clinical Priority Assessment Criteria (CPAC) were developed by professional advisory groups in 1996 as part of the New Zealand health reforms for the purposes of prioritising patients for elective surgery based on an assessment of the level of a patient’s need and ability to benefit from surgery . Similar to the MAPT score, the CPAC assessment tool has seven dimensions that include: clinical, patient-experienced and social measures and these criteria are given points and summed to provide a score from 0 (least priority) to 100 (greatest level of need). A CPAC score threshold above which TJR is indicated is 40 points .
CPAC are widely used across the New Zealand public health system for a variety of elective surgery procedures; however, there is little evidence to support CPAC as an effective tool for prioritising patients for TJR . In a prospective study evaluating CPAC scores in TJR, a weak correlation only was demonstrated between CPAC scores and prioritisation according to need, whereas no significant correlation was demonstrated between CPAC scores and improvement in disease-specific outcome measures . Of concern, the study reported that some patients with moderate or severe problems scored below the thresholds for surgery and the authors suggest that priority criteria, using weighted combinations of clinical and patient-experienced dimensions to give a total score, should probably be abandoned.
Overall, there is little quality evidence to support the use of appropriateness or prioritisation algorithms as referral aids for TJR when they are based on clinical presentation or symptoms alone. This is evidenced by a recent study initiated by the OMERACT/OARSI (Outcome Measures in Rheumatoid Arthritis Clinical Trials and the Osteoarthritis Research Society International) special interest group; a large group of international experts established to propose a definition of severity in lower limb OA that would correspond to a theoretical indication for TJR . In an international cross-sectional study, they found a substantial overlap in symptom levels between patients with and patients without indication for joint replacement. Due to the substantial overlap in pain and function levels between patients with and those without a recommendation for TJR, it was not possible to determine relevant cut points for pain or function, defining recommendation for TJR, even when taking into account the duration of the symptoms or after stratifying by radiographic severity .
Without reliable and reproducible referral aids, physicians are left to base their decision to refer on clinical presentation alone which does not take into account the extent an individual’s risk factors may impact on their capacity to benefit from surgery. However, no referral aids currently exist that take into account individual risk factors and until they are developed and trialled in the primary care setting the level of improvement in pain and function may remain an issue for a significant proportion of individuals undergoing TJR.
Selecting TJR candidates based on disease severity
It is generally recommended that patients with severe symptomatic OA, who have pain that has failed to respond to conservative treatments and who have progressive limitation in activities of daily living should be referred to an orthopaedic surgeon for evaluation . However, opinions about the indications for TJR based on the severity of joint disease and symptomatology vary greatly between referring physicians and surgeons . While there are no universally accepted criteria to determine the indications for TJR, there are algorithms that have been developed to assist with determining appropriateness of surgery based on clinical presentation. Although these algorithms may be used to aid the decision to refer for specialist evaluation, they fail to take into account individual risk factors which may impact on patient outcomes after TJR and few of these algorithms have undergone rigorous evaluation .
Algorithms based on appropriateness criteria
The most widely validated algorithms are those that have used the RAND/UCLA appropriateness method (RAM) , which combines expert opinion with available scientific evidence to create explicit criteria for the appropriateness of a medical or surgical intervention . Quintana et al. and Escobar et al. have developed explicit criteria for hip and knee replacement, respectively, based on this method. Appropriateness is defined as meaning that the expected health benefit exceeds the expected negative consequences by a sufficiently wide margin to make a treatment worth performing .
Quintana et al. developed explicit criteria for appropriateness in total hip replacement (THR) based on a comprehensive list of indications for THR which were initially derived from an extensive literature review . Individual patient variables included: age, bone quality, surgical risk, prior non-surgical procedures performed and pain and functional limitation with each variable categorised based on accepted classification systems published in the literature. All possible combinations of these variables and categories ( n = 216) were reviewed by expert panels who rated appropriateness for surgery for each of the 216 indications using a modified Delphi process. Each scenario was rated as appropriate, uncertain or inappropriate.
To determine the validity of the panel’s findings, a random cohort of patients undergoing THR completed the Western Ontario and McMaster Universities Arthritis Index (WOMAC) , a disease-specific questionnaire, and the SF-36 , a generic health questionnaire, prior to and 3 months after surgery. Patients were classified into one of the three appropriateness groups (appropriate, uncertain and inappropriate) and the improvement in health scores was assessed for each group. Significantly greater improvements in scores were demonstrated for those who were considered appropriate for surgery compared to those considered inappropriate and the differences were clinically meaningful.
Quintana’s appropriateness criteria are expressed as a regression tree which outlines six broad scenarios where referral for consideration for THR would be deemed appropriate ( Table 1 ). For a complete view of the decision tree including appropriate, uncertain and inappropriate scenarios, see Quintana et al. . The evaluation of appropriateness for THR is initially based on the degree of pain on presentation. Where pain is severe and prior conservative measures have been undertaken correctly, THR is deemed appropriate in those with functional limitation, whether minor moderate or severe. In cases where a conservative treatment path has not been followed correctly, surgery is only deemed appropriate in those with severe functional limitation. In those whom pain is mild to moderate and prior conservative treatments have been undertaken correctly, surgery is deemed appropriate for those with severe functional limitation and low surgical risk.
| Pain a | Prior conservative treatment undertaken a | Functional Limitation a | American Society of Anaesthesiologist (ASA) Score a |
|---|---|---|---|
| Mild | Correctly | Severe | 1–3 |
| Moderate | Correctly | Severe | 1–3 |
| Severe | Correctly | Minor | Not required |
| Severe | Correctly | Moderate | Not required |
| Severe | Correctly | Severe | Not required |
| Severe | Incorrectly | Severe | Not required |
a For classification definitions of variables in the algorithm, see appendix in Quintana et al. .
Using a similar process, Escobar et al. have used the RAND method to develop explicit criteria for appropriateness in total knee replacement (TKR), with a few notable differences; radiographic assessment is included in the TKR algorithm and the analyses exclude those who have undergone prior surgical management, arthroscopy and/or tibial osteotomy . Initially, there were 864 indications for TKR identified through a literature review which was reduced to 624 as a result of modifying the variables included and finally 156 of the most frequent scenarios were reviewed by an expert panel for appropriateness assessment. For a complete view of the decision tree including appropriate, uncertain and inappropriate scenarios, see Escobar et al. .
For TKR, surgery was only determined to be appropriate in those with intense to severe pain using a defined set of criteria ( Table 2 ). In those with severe pain and Ahlback classification of I, surgery was deemed appropriate in those who were aged 66 years or older with limited mobility. In those with both intense or severe pain and Ahlback classification of II–III, surgery was deemed appropriate in those aged 55 years or older with limited mobility, whereas in those with Ahlback classification of IV–V, surgery was deemed appropriate in those aged 55 years or older irrespective of mobility. In those younger than 55 years of age with Ahlback classification of IV–V, surgery was only deemed appropriate in those with bicompartmental involvement (including the patella–femoral joint) or tricompartmental OA and again this was irrespective of mobility status.
| Pain a | Ahlback a | Age a | Mobility a | Compartmental involvement a |
|---|---|---|---|---|
| Severe | I | >65 years | Limited | Not required |
| Intense–severe | II–III | ≥55 years | Limited | Not required |
| Intense–severe | IV–V | ≥55 years | Not required | Not required |
| Intense–severe | IV–V | <55 years | Not required | Bicompartmental |
| Intense–severe | IV–V | <55 years | Not required | Tricompartmental |
a For classification definitions of variables in the algorithm, refer Escobar et al. .
While the above algorithms have undergone a validation process , several limitations diminish their usefulness as a clinical guide for specialist referral and these warrant mentioning. The THR algorithm does not take into account radiographic severity, which has, in recent literature, been revealed as an important predictor of the THR outcome in the short and longer term . The use of the American Society of Anaesthesiologist (ASA) score designed for anaesthesiologists to classify surgical risk may restrict the tool’s usefulness in the primary care setting. The algorithm for TKR excludes those who have undergone prior surgical management, diminishing its broad applicability to the population who present with late-stage knee OA, given that arthroscopy is common in the preceding 1–2 years amongst those presenting for TKR .
The most notable limitation with these tools, however, is acknowledged by the authors and, that is, a significant proportion of scenarios are classified by the expert panel as ‘uncertain’ in terms of appropriateness for TJR and for the uncertain group, there were similar improvements in health status and symptom relief as for the group deemed appropriate candidates for surgery . This suggests that a decision to refer for orthopaedic consultation based solely on the appropriateness algorithm would disadvantage a substantial proportion of individuals who may otherwise derive benefit from TJR.
Algorithms based on prioritisation
The Multi-attribute Arthritis Prioritisation Tool (MAPT) score is used as a tool to prioritise the management and care of patients with OA of the hip or knee waiting for primary THR or TKR surgery . The MAPT consists of a series of 11 questions that are answered by the patient. It aims to assess the severity of pain, functional disability, psychological health, economic impact and deterioration in those with hip or knee symptoms. Higher MAPT scores suggest higher perceived disability and pain by the patient and should trigger earlier referral to a specialist clinic or prioritisation for surgery . MAPT can be used to facilitate fast-tracking of patients with the greatest need for TJR, monitoring for deterioration in those waiting for surgery or having a trial of non-operative treatment and deferment of surgery for those who may benefit from further non-operative treatments .
The MAPT is routinely administered in hospitals across Victoria, Australia, but there is a lack of evidence that the prioritisation for TJR surgery according to MAPT scores correlates with response to surgery. One study of patients on the waiting list for TJR demonstrated that there is no correlation between MAPT scores and radiographic severity of arthritis. David et al. found that the mean MAPT score was higher (80.76) in patients with a lower Kellgren–Lawrence (KL) radiographic grade of arthritis (grade 1 or 2) than the mean MAPT score (60.17) in patients with a higher radiographic grade of arthritis (grade 3 or 4). A MAPT score of 21–60 is considered middle priority, whereas a score >60 is considered highest priority indicating that surgery is warranted in the immediate term . These findings suggest that using the MAPT score to aid the decision for specialist referral or to prioritise for surgery without consideration of radiographic severity may lead to TJR surgery being undertaken in individuals with early OA where conservative treatment is warranted.
The Clinical Priority Assessment Criteria (CPAC) were developed by professional advisory groups in 1996 as part of the New Zealand health reforms for the purposes of prioritising patients for elective surgery based on an assessment of the level of a patient’s need and ability to benefit from surgery . Similar to the MAPT score, the CPAC assessment tool has seven dimensions that include: clinical, patient-experienced and social measures and these criteria are given points and summed to provide a score from 0 (least priority) to 100 (greatest level of need). A CPAC score threshold above which TJR is indicated is 40 points .
CPAC are widely used across the New Zealand public health system for a variety of elective surgery procedures; however, there is little evidence to support CPAC as an effective tool for prioritising patients for TJR . In a prospective study evaluating CPAC scores in TJR, a weak correlation only was demonstrated between CPAC scores and prioritisation according to need, whereas no significant correlation was demonstrated between CPAC scores and improvement in disease-specific outcome measures . Of concern, the study reported that some patients with moderate or severe problems scored below the thresholds for surgery and the authors suggest that priority criteria, using weighted combinations of clinical and patient-experienced dimensions to give a total score, should probably be abandoned.
Overall, there is little quality evidence to support the use of appropriateness or prioritisation algorithms as referral aids for TJR when they are based on clinical presentation or symptoms alone. This is evidenced by a recent study initiated by the OMERACT/OARSI (Outcome Measures in Rheumatoid Arthritis Clinical Trials and the Osteoarthritis Research Society International) special interest group; a large group of international experts established to propose a definition of severity in lower limb OA that would correspond to a theoretical indication for TJR . In an international cross-sectional study, they found a substantial overlap in symptom levels between patients with and patients without indication for joint replacement. Due to the substantial overlap in pain and function levels between patients with and those without a recommendation for TJR, it was not possible to determine relevant cut points for pain or function, defining recommendation for TJR, even when taking into account the duration of the symptoms or after stratifying by radiographic severity .
Without reliable and reproducible referral aids, physicians are left to base their decision to refer on clinical presentation alone which does not take into account the extent an individual’s risk factors may impact on their capacity to benefit from surgery. However, no referral aids currently exist that take into account individual risk factors and until they are developed and trialled in the primary care setting the level of improvement in pain and function may remain an issue for a significant proportion of individuals undergoing TJR.
Related posts:
The epidemiology of osteoarthritis
The role of imaging in osteoarthritis
Biomarkers for osteoarthritis: Current position and steps towards further validation
Patellofemoral joint osteoarthritis: An individualised pathomechanical approach to management
Pathogenesis of post-traumatic OA with a view to intervention
Chronic disease management: Improving care for people with osteoarthritis
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