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The patellofemoral joint: the forgotten joint in knee osteoarthritis
Osteoarthritis and Cartilage 19 (2011) 765–767
Editorial
The patellofemoral joint: the forgotten joint in knee osteoarthritis
Keywords: Patella Arthritis Biomechanics Rehabilitation
The current issue of Osteoarthritis and Cartilage contains two manuscripts devoted to the patellofemoral (PF) joint. This is notable, since the PF compartment is rarely considered in investigations of osteoarthritis (OA), despite accounting for approximately 65% of persons with symptomatic knee OA1. Most importantly, the PF joint is more likely than the tibiofemoral joint to result in knee OA symptoms2, and even isolated mild radiographic PF OA can cause considerable symptoms that impact substantially on activities of daily living2,3. Yet, surprisingly, we know little about PF OA, particularly the factors that contribute to its development and, most importantly, how to effectively manage this common and potentially debilitating condition. PF pain syndrome (presenting in younger adults as anterior or retropatellar pain in the presence of activities that load the PF joint) is no longer considered to be self-limiting and may be related to the development of PF OA4. Therefore, we can increase our understanding of PF OA by extrapolating from the more extensive literature investigating PF pain syndrome. Altered mechanical load contributes to OA development and progression and a recent issue of Osteoarthritis and Cartilage, identified that individuals with PF pain syndrome had greater PF stress than asymptomatic controls5. This increased stress could represent an important link between PF pain in younger adults and the persistence or progression of pain and/or structural joint disease. Malalignment of the patella relative to the femoral trochlea influences both the magnitude and the distribution of PF forces. In the few studies investigating PF OA, lateral patellar malalignment has been identified as a feature of PF OA6,7 and as a risk factor for PF OA progression8. Importantly, due to the unique structure and function of the PF joint, motions of the tibiofemoral joint (particularly valgus and external rotation) will influence PF joint alignment and loading. Valgus tibiofemoral malalignment increases the load on the lateral patella facet and is associated with the presence and progression of radiographic PF OA (as opposed to the varus malalignment seen with tibiofemoral OA)9. Tibiofemoral external rotation (femoral internal rotation or tibial external rotation) increases lateral PF malalignment and stress10 and hence, is likely to be important in PF OA. While bony
morphologies contribute strongly to movements and alignments of the PF and tibiofemoral joints, non-structural factors (e.g., joint soft tissues and muscles) are also important and may be more amenable to modification. Based on cadaveric and modelling studies, interventions with the potential to reduce stress on the lateral PF joint include reducing patellar malalignment via taping/ bracing or enhancing vastus medialis function (relative to the vastus lateralis), and reducing knee valgus and/or knee external rotation through retraining of pelvis and hip muscle function10. Despite clinical guidelines emphasising the importance of tailored OA management strategies for optimal clinical outcome, scant research has evaluated conservative treatments specific to patients with PF OA. Of the few trials conducted to date, patellar taping appears to result in immediate and short-term reductions in knee pain6,11, whilst a multi-faceted physiotherapy program offers no long-term benefits12. Thus, in contrast to tibiofemoral OA, there is little evidence available to guide effective management of PF OA. In this issue of Osteoarthritis and Cartilage, Hunter et al.13 report the results of a double-blind randomized crossover trial evaluating a realigning PF brace in people with symptomatic lateral PF OA. This study is a valuable addition to the limited body of knowledge in this area. Given the short-term benefits of patellar tape, mechanical realignment of the patella with a brace constitutes a logical treatment for this condition. The failure of this study to demonstrate any beneficial clinical effect of the brace is disappointing, although perhaps not entirely surprising given that similar braces have disputable evidence for their benefit in PF pain in younger adults without OA14. It is unclear why this is so. Clinical trials of patellar bracing require patients to don the brace independently and it is unknown how successful patients are at appropriately applying such a brace. Furthermore, patient adherence with bracing is an important consideration. Although Hunter et al.13 reported compliance with the prescribed 4 h of daily brace use, it is possible that this treatment duration is too short to reduce knee symptoms. It is also possible that the realigning braces did not realign the patella sufficiently, or that any immediate changes in patellar alignment with bracing were not sustained over the course of the day
1063-4584/$ – see front matter Ó 2011 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.joca.2011.05.005
766
Editorial / Osteoarthritis and Cartilage 19 (2011) 765–767
during prolonged use. In this issue of Osteoarthritis and Cartilage, McWalter and co-workers15 measure the effects of the patellar brace employed by Hunter et al.13 on patellar alignment. The authors used reliable and valid magnetic resonance imaging methods to determine the three-dimensional kinematics of the patella, thus overcoming the problems associated with traditional marker-based methods of measuring patellar kinematics and improving on the twodimensional methods employed in most imaging studies. This study observed statistically significant changes in patellar kinematics with the brace. However, the changes were very small in magnitude, and it is not clear whether the changes are greater than the reported measurement error presented in the paper, or if they are sufficient to provide a clinical benefit. Combined, the results from the two patellar brace papers reinforce the multi-factorial nature of OA-associated pain, and the imprecise relationship between patellar malalignment and symptom severity in PF OA. Thus, other factors that can influence PF stress (e.g., hip or vasti function) or alter pain perception need to be considered in this patient subgroup. It is also important to note that both treatment groups improved in the study by Hunter et al.13. However, in the absence of a “no-treatment control” group, it is impossible to tell whether these changes were due to a placebo effect or natural history, or whether the compression that was common to both braces had a direct beneficial treatment effect. The papers in this current issue highlight some of the difficulties in developing treatment strategies for PF OA. One impediment is the lack of consensus on diagnostic criteria for PF OA. Presently, researchers tend to rely on a combination of features from radiographic and clinical assessment. Most radiographic scoring systems were originally developed for evaluating the tibiofemoral compartments and thus may not be reliable or valid for the PF joint. Further, little is known about how best to separate PF symptoms from those arising from the tibiofemoral joint. If we are unable to accurately classify patients with PF OA, it is difficult to increase our understanding of the features and impairments associated with the disease in order to develop targeted interventions. The problem of patient classification is compounded for many (if not most) cases, where PF OA occurs in combination with tibiofemoral disease. Should patients with isolated PF OA be considered a different sub-group to those with concurrent tibiofemoral OA? This becomes an important issue when choosing treatment strategies for people with mixed compartment disease. For example, given that increasing knee valgus malalignment is associated with progression of PF OA9, it could appear reasonable to employ a brace designed to increase knee varus. However, such a strategy would be detrimental for the medial tibiofemoral compartment given that increasing knee varus is typically associated with structural deterioration in this compartment. In light of the difficulties associated with the classification of PF OA and knowledge of appropriate interventions, more research is urgently required. Current treatment paradigms for PF OA are inadequate. Conservative interventions are the first line management for knee OA and are critical for PF OA, given that surgical options are limited in availability and efficacy. Whilst joint replacement surgery is efficacious and cost effective for tibiofemoral OA, PF arthroplasty or resurfacing procedures are associated with only modest outcomes at best16,17. Furthermore, published guidelines are based exclusively on research utilising participants with tibiofemoral OA, not those with predominant PF OA. It is inappropriate to assume that treatments designed for tibiofemoral OA are optimal for PF OA. We know that altered PF loading leads to symptoms and structural progression. Extending from this, treatments targeted at reducing PF stress are likely to reduce symptoms and slow disease progression. Such interventions may include quadriceps strengthening, vastus medialis retraining, gluteal or trunk muscle retraining, foot
orthoses, patellar taping and/or bracing, and need to be tested in rigorous clinical trials. Author contributions This editorial was written by Kay M Crossley and Rana S Hinman. Both authors contributed to the editing and approval of this work. Role of funding source No funding source had a role in this editorial. Conflict of interest KMC and RSH do not have any conflicts of interest to declare. Acknowledgements KMC and RSH do not receive direct funding from external sources. References 1. Duncan R, Hay E, Saklatvala J, Croft P. Prevalence of radiographic osteoarthritis: it all depends on your point of view. Rheumatology 2006;45(6):757–60. 2. Duncan R, Peat G, Thomas E, Wood L, Hay E, Croft P. How do pain and function vary with compartmental distribution and severity of radiographic knee osteoarthritis? Rheumatology 2008;47:1704–7. 3. Duncan R, Peat G, Thomas E, Wood LEH, Croft P. Does isolated patellofemoral osteoarthritis matter? Osteoarthritis Cartilage 2009;17(9):1151–5. 4. Thomas MJ, Wood L, Selfe J, Peat G. Anterior knee pain in younger adults as a precursor to subsequent patellofemoral osteoarthritis: a systematic review. BMC Musculoskelet Disord 2010;11:201. 5. Farrokhi S, Keyak JH, Powers CM. Individuals with patellofemoral pain exhibit greater patellofemoral joint stress: a finite element analysis study. Osteoarthritis Cartilage 2011;19(3):287–94. 6. Crossley KM, Marino GP, Macilquham MD, Schache AG, Hinman RS. Can patellar tape reduce patellar malalignment and pain associated with patellofemoral osteoarthritis? Arthritis Rheum 2009;61(12):1719–25. 7. Kalichman L, Zhang Y, Niu J, Goggins J, Gale D, Felson DT, et al. The association between patellar alignment and patellofemoral joint osteoarthritis features – an MRI study. Rheumatology 2007;46(8):1303–8. 8. Hunter DJ, Zhang YQ, Niu JB, Felson DT, Kwoh K, Newman A, et al. Patella malalignment, pain and patellofemoral progression: the health ABC study. Osteoarthritis Cartilage 2007; 15(10):1120–7. 9. Hinman RS, Crossley KM. Patellofemoral osteoarthritis: an important subgroup of knee osteoarthritis. Rheumatology 2007;46(7):1057–62. 10. Powers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther 2010;40(2):42–51. 11. Cushnaghan J, McCarthy C, Dieppe P. Taping the patella medially: a new treatment for osteoarthritis of the knee joint? BMJ 1994;308:753–5. 12. Quilty B, Tucker M, Campbell R, Dieppe P. Physiotherapy, including quadriceps exercises and patellar taping, for knee osteoarthritis with predominant patellofemoral involvement: randomized controlled trial. J Rheumatol 2003;30:1311–7.
Editorial / Osteoarthritis and Cartilage 19 (2011) 765–767
13. Quilty B, Tucker M, Campbell R, Dieppe P. Physiotherapy, including quadriceps exercises and patellar taping, for knee osteoarthritis with predominant patellofemoral involvement: randomized controlled trial. Journal of Rheumatology 2003; 30:1311–7. 14. Warden SJ, Hinman RS, Watson MAJ, Avin KG, Bialocerkowski AE, Crossley KM. Patellar taping and bracing for the treatment of chronic knee pain: a systematic review and meta-analysis. Arthritis Rheum 2008;59:78–83. 15. McWalter EJ, Hunter DJ, Harvey WF, McCree P, Hirko KA, Wilson DR. The effect of a patellar brace on threedimensional patellar kinematics in patients with lateral patellofemoral osteoarthritis. Osteoarthritis Cartilage 2011. 16. Leadbetter WB. Patellofemoral arthroplasty in the treatment of patellofemoral arthritis: rationale and outcomes in younger patients. Orthopaedic Clinics of North America 2008;39: 363–80.
767
17. Nizard RS, Biau D, Porcher R, Ravaud P, Bizot P, Hannouche D, et al. A meta-analysis of patellar replacement in total knee arthroplasty. Clinical Orthopaedics and Related Research 2005; 432:196–203. K.M. Crossleyyz*, R.S. Hinmanz yDepartment of Mechanical Engineering, Melbourne School of Engineering, The University of Melbourne, Melbourne, Australia zSchool of Physiotherapy, The University of Melbourne, Melbourne, Australia * Address correspondence and reprint requests to: K.M. Crossley, Department of Mechanical Engineering, Melbourne School of Engineering, The University of Melbourne, Parkville 3010, Melbourne, Australia. Tel: 61-3-8344-8646; Fax: 61-3-8344-4290. E-mail address: [email protected] (K.M. Crossley)
Editorial
The patellofemoral joint: the forgotten joint in knee osteoarthritis
Keywords: Patella Arthritis Biomechanics Rehabilitation
The current issue of Osteoarthritis and Cartilage contains two manuscripts devoted to the patellofemoral (PF) joint. This is notable, since the PF compartment is rarely considered in investigations of osteoarthritis (OA), despite accounting for approximately 65% of persons with symptomatic knee OA1. Most importantly, the PF joint is more likely than the tibiofemoral joint to result in knee OA symptoms2, and even isolated mild radiographic PF OA can cause considerable symptoms that impact substantially on activities of daily living2,3. Yet, surprisingly, we know little about PF OA, particularly the factors that contribute to its development and, most importantly, how to effectively manage this common and potentially debilitating condition. PF pain syndrome (presenting in younger adults as anterior or retropatellar pain in the presence of activities that load the PF joint) is no longer considered to be self-limiting and may be related to the development of PF OA4. Therefore, we can increase our understanding of PF OA by extrapolating from the more extensive literature investigating PF pain syndrome. Altered mechanical load contributes to OA development and progression and a recent issue of Osteoarthritis and Cartilage, identified that individuals with PF pain syndrome had greater PF stress than asymptomatic controls5. This increased stress could represent an important link between PF pain in younger adults and the persistence or progression of pain and/or structural joint disease. Malalignment of the patella relative to the femoral trochlea influences both the magnitude and the distribution of PF forces. In the few studies investigating PF OA, lateral patellar malalignment has been identified as a feature of PF OA6,7 and as a risk factor for PF OA progression8. Importantly, due to the unique structure and function of the PF joint, motions of the tibiofemoral joint (particularly valgus and external rotation) will influence PF joint alignment and loading. Valgus tibiofemoral malalignment increases the load on the lateral patella facet and is associated with the presence and progression of radiographic PF OA (as opposed to the varus malalignment seen with tibiofemoral OA)9. Tibiofemoral external rotation (femoral internal rotation or tibial external rotation) increases lateral PF malalignment and stress10 and hence, is likely to be important in PF OA. While bony
morphologies contribute strongly to movements and alignments of the PF and tibiofemoral joints, non-structural factors (e.g., joint soft tissues and muscles) are also important and may be more amenable to modification. Based on cadaveric and modelling studies, interventions with the potential to reduce stress on the lateral PF joint include reducing patellar malalignment via taping/ bracing or enhancing vastus medialis function (relative to the vastus lateralis), and reducing knee valgus and/or knee external rotation through retraining of pelvis and hip muscle function10. Despite clinical guidelines emphasising the importance of tailored OA management strategies for optimal clinical outcome, scant research has evaluated conservative treatments specific to patients with PF OA. Of the few trials conducted to date, patellar taping appears to result in immediate and short-term reductions in knee pain6,11, whilst a multi-faceted physiotherapy program offers no long-term benefits12. Thus, in contrast to tibiofemoral OA, there is little evidence available to guide effective management of PF OA. In this issue of Osteoarthritis and Cartilage, Hunter et al.13 report the results of a double-blind randomized crossover trial evaluating a realigning PF brace in people with symptomatic lateral PF OA. This study is a valuable addition to the limited body of knowledge in this area. Given the short-term benefits of patellar tape, mechanical realignment of the patella with a brace constitutes a logical treatment for this condition. The failure of this study to demonstrate any beneficial clinical effect of the brace is disappointing, although perhaps not entirely surprising given that similar braces have disputable evidence for their benefit in PF pain in younger adults without OA14. It is unclear why this is so. Clinical trials of patellar bracing require patients to don the brace independently and it is unknown how successful patients are at appropriately applying such a brace. Furthermore, patient adherence with bracing is an important consideration. Although Hunter et al.13 reported compliance with the prescribed 4 h of daily brace use, it is possible that this treatment duration is too short to reduce knee symptoms. It is also possible that the realigning braces did not realign the patella sufficiently, or that any immediate changes in patellar alignment with bracing were not sustained over the course of the day
1063-4584/$ – see front matter Ó 2011 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.joca.2011.05.005
766
Editorial / Osteoarthritis and Cartilage 19 (2011) 765–767
during prolonged use. In this issue of Osteoarthritis and Cartilage, McWalter and co-workers15 measure the effects of the patellar brace employed by Hunter et al.13 on patellar alignment. The authors used reliable and valid magnetic resonance imaging methods to determine the three-dimensional kinematics of the patella, thus overcoming the problems associated with traditional marker-based methods of measuring patellar kinematics and improving on the twodimensional methods employed in most imaging studies. This study observed statistically significant changes in patellar kinematics with the brace. However, the changes were very small in magnitude, and it is not clear whether the changes are greater than the reported measurement error presented in the paper, or if they are sufficient to provide a clinical benefit. Combined, the results from the two patellar brace papers reinforce the multi-factorial nature of OA-associated pain, and the imprecise relationship between patellar malalignment and symptom severity in PF OA. Thus, other factors that can influence PF stress (e.g., hip or vasti function) or alter pain perception need to be considered in this patient subgroup. It is also important to note that both treatment groups improved in the study by Hunter et al.13. However, in the absence of a “no-treatment control” group, it is impossible to tell whether these changes were due to a placebo effect or natural history, or whether the compression that was common to both braces had a direct beneficial treatment effect. The papers in this current issue highlight some of the difficulties in developing treatment strategies for PF OA. One impediment is the lack of consensus on diagnostic criteria for PF OA. Presently, researchers tend to rely on a combination of features from radiographic and clinical assessment. Most radiographic scoring systems were originally developed for evaluating the tibiofemoral compartments and thus may not be reliable or valid for the PF joint. Further, little is known about how best to separate PF symptoms from those arising from the tibiofemoral joint. If we are unable to accurately classify patients with PF OA, it is difficult to increase our understanding of the features and impairments associated with the disease in order to develop targeted interventions. The problem of patient classification is compounded for many (if not most) cases, where PF OA occurs in combination with tibiofemoral disease. Should patients with isolated PF OA be considered a different sub-group to those with concurrent tibiofemoral OA? This becomes an important issue when choosing treatment strategies for people with mixed compartment disease. For example, given that increasing knee valgus malalignment is associated with progression of PF OA9, it could appear reasonable to employ a brace designed to increase knee varus. However, such a strategy would be detrimental for the medial tibiofemoral compartment given that increasing knee varus is typically associated with structural deterioration in this compartment. In light of the difficulties associated with the classification of PF OA and knowledge of appropriate interventions, more research is urgently required. Current treatment paradigms for PF OA are inadequate. Conservative interventions are the first line management for knee OA and are critical for PF OA, given that surgical options are limited in availability and efficacy. Whilst joint replacement surgery is efficacious and cost effective for tibiofemoral OA, PF arthroplasty or resurfacing procedures are associated with only modest outcomes at best16,17. Furthermore, published guidelines are based exclusively on research utilising participants with tibiofemoral OA, not those with predominant PF OA. It is inappropriate to assume that treatments designed for tibiofemoral OA are optimal for PF OA. We know that altered PF loading leads to symptoms and structural progression. Extending from this, treatments targeted at reducing PF stress are likely to reduce symptoms and slow disease progression. Such interventions may include quadriceps strengthening, vastus medialis retraining, gluteal or trunk muscle retraining, foot
orthoses, patellar taping and/or bracing, and need to be tested in rigorous clinical trials. Author contributions This editorial was written by Kay M Crossley and Rana S Hinman. Both authors contributed to the editing and approval of this work. Role of funding source No funding source had a role in this editorial. Conflict of interest KMC and RSH do not have any conflicts of interest to declare. Acknowledgements KMC and RSH do not receive direct funding from external sources. References 1. Duncan R, Hay E, Saklatvala J, Croft P. Prevalence of radiographic osteoarthritis: it all depends on your point of view. Rheumatology 2006;45(6):757–60. 2. Duncan R, Peat G, Thomas E, Wood L, Hay E, Croft P. How do pain and function vary with compartmental distribution and severity of radiographic knee osteoarthritis? Rheumatology 2008;47:1704–7. 3. Duncan R, Peat G, Thomas E, Wood LEH, Croft P. Does isolated patellofemoral osteoarthritis matter? Osteoarthritis Cartilage 2009;17(9):1151–5. 4. Thomas MJ, Wood L, Selfe J, Peat G. Anterior knee pain in younger adults as a precursor to subsequent patellofemoral osteoarthritis: a systematic review. BMC Musculoskelet Disord 2010;11:201. 5. Farrokhi S, Keyak JH, Powers CM. Individuals with patellofemoral pain exhibit greater patellofemoral joint stress: a finite element analysis study. Osteoarthritis Cartilage 2011;19(3):287–94. 6. Crossley KM, Marino GP, Macilquham MD, Schache AG, Hinman RS. Can patellar tape reduce patellar malalignment and pain associated with patellofemoral osteoarthritis? Arthritis Rheum 2009;61(12):1719–25. 7. Kalichman L, Zhang Y, Niu J, Goggins J, Gale D, Felson DT, et al. The association between patellar alignment and patellofemoral joint osteoarthritis features – an MRI study. Rheumatology 2007;46(8):1303–8. 8. Hunter DJ, Zhang YQ, Niu JB, Felson DT, Kwoh K, Newman A, et al. Patella malalignment, pain and patellofemoral progression: the health ABC study. Osteoarthritis Cartilage 2007; 15(10):1120–7. 9. Hinman RS, Crossley KM. Patellofemoral osteoarthritis: an important subgroup of knee osteoarthritis. Rheumatology 2007;46(7):1057–62. 10. Powers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther 2010;40(2):42–51. 11. Cushnaghan J, McCarthy C, Dieppe P. Taping the patella medially: a new treatment for osteoarthritis of the knee joint? BMJ 1994;308:753–5. 12. Quilty B, Tucker M, Campbell R, Dieppe P. Physiotherapy, including quadriceps exercises and patellar taping, for knee osteoarthritis with predominant patellofemoral involvement: randomized controlled trial. J Rheumatol 2003;30:1311–7.
Editorial / Osteoarthritis and Cartilage 19 (2011) 765–767
13. Quilty B, Tucker M, Campbell R, Dieppe P. Physiotherapy, including quadriceps exercises and patellar taping, for knee osteoarthritis with predominant patellofemoral involvement: randomized controlled trial. Journal of Rheumatology 2003; 30:1311–7. 14. Warden SJ, Hinman RS, Watson MAJ, Avin KG, Bialocerkowski AE, Crossley KM. Patellar taping and bracing for the treatment of chronic knee pain: a systematic review and meta-analysis. Arthritis Rheum 2008;59:78–83. 15. McWalter EJ, Hunter DJ, Harvey WF, McCree P, Hirko KA, Wilson DR. The effect of a patellar brace on threedimensional patellar kinematics in patients with lateral patellofemoral osteoarthritis. Osteoarthritis Cartilage 2011. 16. Leadbetter WB. Patellofemoral arthroplasty in the treatment of patellofemoral arthritis: rationale and outcomes in younger patients. Orthopaedic Clinics of North America 2008;39: 363–80.
767
17. Nizard RS, Biau D, Porcher R, Ravaud P, Bizot P, Hannouche D, et al. A meta-analysis of patellar replacement in total knee arthroplasty. Clinical Orthopaedics and Related Research 2005; 432:196–203. K.M. Crossleyyz*, R.S. Hinmanz yDepartment of Mechanical Engineering, Melbourne School of Engineering, The University of Melbourne, Melbourne, Australia zSchool of Physiotherapy, The University of Melbourne, Melbourne, Australia * Address correspondence and reprint requests to: K.M. Crossley, Department of Mechanical Engineering, Melbourne School of Engineering, The University of Melbourne, Parkville 3010, Melbourne, Australia. Tel: 61-3-8344-8646; Fax: 61-3-8344-4290. E-mail address: [email protected] (K.M. Crossley)