Description of the condition
The term 'patellofemoral pain syndrome' (PFPS) is associated with retropatellar (behind the knee cap) pain (Grelsamer 2009). This term has been used interchangeably with other terms, most notably anterior knee pain and patellofemoral syndrome (Grelsamer 2009). It is more commonly seen in females than in males, and has an estimated prevalence of 12% to 45% amongst young, physically active people (Bizzini 2003; Cook 2010; Dixit 2007; Roush 2012). This wide variation has been attributed to the diversity of people who may experience this condition; from sedentary adolescents to military recruits during basic training (Callaghan 2007). PFPS is characterised by pain behind and around the patella, which is aggravated during prolonged sitting, descending stairs or slopes, squatting or kneeling (Dixit 2007; Grelsamer 2009).
The aetiology of PFPS remains unclear (Lankhorst 2012; Waryasz 2008). However, the basic premise is that the patella 'moves' abnormally within the femoral trochlear (groove-shaped part of the thigh bone at the knee). This is termed maltracking. The patella most frequently maltracks laterally (sideways) and therefore tries to deviate and move against the outside border of the femoral trochlear. Repetitive maltracking is associated with increased sheering and compressive forces between the retropatellar and femoral trochlear articulation (Song 2011; Waryasz 2008). The causes of maltracking are largely acknowledged to be multifactorial. Factors that may contribute to this include lateral retinaculum shortening (Hudson 2009), an imbalance between the activation and intensity of vastus lateralis and vastus medialis muscles (Chester 2008), reduced hip muscle control (Barton 2013; Cowan 2009), hamstring, quadriceps or calf muscle tightness (Erkula 2002; Waryasz 2008), excessive tibial external rotation from foot pronation (Barton 2011), femoral anteversion (Keser 2008) and trochlear dysplasia (Parikh 2011).
The diagnosis of PFPS is usually derived from a person's reported history and their symptoms. A physical examination is important to exclude other injuries such as meniscal or ligament tear, tendinopathy, fracture and dislocation (Dixit 2007). Physical examination is also necessary in order to assess the various different factors, listed above, that might contribute to the presentation.
In part reflecting the multifactorial nature of PFPS, a number of different interventions have been advocated. These include: quadriceps strengthening and stretching exercises (Chiu 2012), patellar adhesive taping and biofeedback exercises (Cowan 2002), foot orthotics (Barton 2010), manual therapy (Brantingham 2012), acupuncture (Jensen 1999) and knee orthoses (Bizzini 2003; Powers 2004).
Description of the intervention
This review will examine the use of knee orthoses for people with PFPS. Knee orthoses are essentially external, non-adhesive devices which aim to modify the position of the patella. The term 'knee orthosis' encompasses a variety of different interventions including knee braces, sleeves, bandages or straps. They are frequently made of neoprene and are available in a variety of sizes to account for different limb circumferences (Shellock 2000). The majority of orthoses have a 'patella hole', which is a hole cut out of the neoprene sleeve. In addition, in some designs, a strap or buttress is incorporated into the orthosis. These features are intended to help keep the patella in a more central position (Chew 2007).
Knee orthoses have been described as simple, inexpensive, and associated with negligible adverse effects (Warden 2008). People can purchase these independently, or they may be prescribed by a healthcare professional. The user can apply the knee orthosis without assistance, which allows them greater control over managing their knee condition. Knee orthoses can be worn during normal activities of daily living, as well as during sporting and occupational pursuits. There is no consensus as to whether bracing should be used as an adjunct to treatment or on its own for the treatment of pain for those with PFPS (Dixit 2007).
How the intervention might work
Whilst consensus regarding the aetiology of PFPS is lacking, abnormal patellar tracking is largely considered to be the primary cause (Powers 2004). It has been suggested that knee orthoses work by centralising the patella within the femoral trochlea, thereby correcting abnormal patellar tracking and reducing pain (Powers 2004). However, whilst some studies have provided support that knee orthoses can alter patellar alignment (Shellock 1994; Shellock 2000), others have reported the contrary during radiological investigations (Muhle 1999; Powers 1999; Powers 2004).
Knee orthoses may also have other therapeutic effects. For instance, wearing the neoprene orthosis may have a thermal effect, which could increase sensory feedback and proprioception, while also altering knee circulation (Herrington 2005; Shellock 1995; Van Tiggelen 2004). Finally, Earl 2004 reported that knee orthoses work by 'unloading' the patellofemoral joint when orthoses are used during exercise compared with not wearing a brace. They postulated that a knee orthosis, by reducing contact forces between the patella and the femoral trochlea, may therefore reduce the symptoms related to PFPS. Through this symptomatic relief, it is speculated that knee orthosis can facilitate greater exercise tolerance and capability, thus optimising the clinical effects of exercise (Swart 2012).
Why it is important to do this review
The use of knee orthoses has been widely documented in the literature for assisting the management of people with PFPS. However, no systematic reviews have rigorously assessed their application for this population. There remains mixed evidence as to the effectiveness of knee orthoses for this population.
Patellofemoral pain syndrome is acknowledged as a potentially disabling condition, which can impact on the occupational and sporting pursuits of children and young adults. Furthermore, previous authors have acknowledged a link between adolescent PFPS and the development of patellofemoral osteoarthritis (Thomas 2010; Utting 2005). Given this impact, both in the short- and potentially longer-term, and limited consensus in the effectiveness of knee orthoses, this review is important to better inform clinicians and the public on the use of these interventions for treating this musculoskeletal condition.
To assess the effects (benefits and harms) of knee orthoses (knee brace, sleeve, bandage or strap) for treating PFPS.
Criteria for considering studies for this review
Types of studies
We will include randomised and quasi-randomised (method of allocating participants to a treatment which is not strictly random: e.g. by hospital number) controlled clinical trials evaluating knee orthoses for treating patellofemoral pain syndrome. Cross-over study designs will be excluded due to the potential for treatment 'carry-over' from one randomised arm to another, irrespective of the duration of the 'wash-out' period.
Types of participants
Trials including participants subjectively reporting pain diagnosed by authors as 'patellofemoral pain syndrome', 'anterior knee pain syndrome', 'patellar dysfunction', 'chondromalacia patellae', 'patellar syndrome', 'patellofemoral syndrome' or 'chondropathy', will be included. No restriction will be placed on the age of the participant, duration of symptoms or stage of disease, although these variables may be analysed as subgroups.
Trials where participants were asymptomatic or non-pathological will be excluded. Trials which recruit participants with a history of fracture, patellar dislocation, patellar tendinopathy, Hoffa's syndrome, Osgood Schlatter syndrome, Sinding-Larsen-Johansson syndrome, iliotibial band friction syndrome, osteoarthritis, rheumatoid arthritis, plica syndromes, or tibiofemoral injury or dysfunction will also be excluded.
Trials reporting the use of orthoses following operative interventions (either immediately post-operatively or at any point following surgery) will be excluded.
Trials including mixed population trials where a percentage of the cohort may have some other (possibly undiagnosed) knee pathology, such as patellar tendinopathy, will be excluded unless the results for the PFPS cohort are presented separately or the numbers of such 'undiagnosed' patients are small and sufficiently balanced between the intervention groups.
Types of interventions
We will include trials evaluating the use of a knee orthosis. A knee orthosis will be defined as a device that aims to control or change patellar tracking and/or loading, and may take the form of a knee brace, sleeve, bandage or straps.
Comparisons will include:
- Knee orthosis versus no treatment
- Knee orthosis and non-operative intervention (e.g. exercise) versus non-operative intervention alone
- One type of knee orthosis versus another
- Knee orthosis versus another non-operative intervention (e.g. exercise)
- Mode of knee orthosis use: e.g. length of time worn per day; whether orthosis is only worn during physical activity versus all day.
Trials looking at taping techniques will not be included as they have been assessed in another Cochrane Review (Callaghan 2012).
Types of outcome measures
The following primary and secondary outcome measures will be assessed.
- Pain during activity or at rest, measured using a visual analogue scale (VAS) or similar, preferably at 12 months follow-up post-commencing the intervention. Pain may be assessed during a specific activity (e.g. single leg squat), or more globally as usual pain during the previous week.
- Impact on sporting or occupational participation: e.g. duration of occupational sick leave, or time to return to sports at the same pre-injury level.
- Resources use/costs of intervention.
- Participant satisfaction: e.g. Likert scale, VAS or any other validated score.
- Complications to orthoses: e.g. allergies or subsequent injury.
Biomechanical outcomes such as postural sway, joint proprioception, force-plate distribution and muscle dynamometry will not be included in this review.
Inclusion of one or more of the listed outcomes is a prerequisite for study inclusion in the review.
Timing of outcome assessment
For each outcome, the primary end-point for analysis will be 12 months. However, short-term (0 to 3 months), medium-term (3 months to 12 months) and longer-term (over 12 months) analyses will also be conducted.
Search methods for identification of studies
We will search the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, the Cochrane Central Register of Controlled Trials (The Cochrane Library, Wiley Online Library), MEDLINE (OvidSP), EMBASE (OvidSP), SportDiscus (EBSCO), Allied and Complementary Medicine (AMED) (OvidSP), the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (NHS Evidence), and the Physiotherapy Evidence Database (PEDro). All databases will be searched from their inception to present. There will be no restrictions on language, date or publication status.
Trial registry and grey literature evidence-bases including the WHO International Clinical Trials Registry Platform, Current Controlled Trials, ClinicalTrials.gov and OpenGrey (System for Information on Grey Literature in Europe) will be reviewed for ongoing or unpublished trials.
In MEDLINE, a subject-specific search will be combined with the Cochrane Highly Sensitive Search Strategy to identify randomised trials (sensitivity-maximizing version), as described by Lefebvre 2011 (see Appendix 1). This will be adapted for the other databases.
Searching other resources
The reference lists of all pertinent review papers and eligible trials will be scrutinised. The corresponding authors for all eligible trials will be contacted for further data.
Conference proceedings and abstracts from the British Orthopaedic Association Annual Congress, the European Federation of National Associations of Orthopaedics and Traumatology (EFORT), World Sports Trauma Congress (WSTC) and the British Association for Surgery of the Knee will be searched. These will be accessed by The Bone & Joint Journal Orthopaedic Proceedings.
Data collection and analysis
Selection of studies
Two review authors (TS and BD) will independently review the titles and abstracts of the search strategy results to identity all potentially eligible trials, for which full text reports will be sought. The same two authors will independently perform study selection. Any disagreements will be resolved through discussion, adjudicated if necessary by a third review author (AC), until a consensus is reached.
Data extraction and management
Two review authors (TS and BD) will independently review and extract data from each included trial. Any disagreements will be resolved through discussion, adjudicated if necessary by a third review author (AC), until a consensus is reached.
Assessment of risk of bias in included studies
Two review authors (TS and BD) will independently assess the risk of bias of the included trials using The Cochrane Collaboration's 'Risk of bias' tool (Higgins 2011a). The following domains will be evaluated: sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, completeness of outcome data reporting, selective outcome reporting and other sources of bias if identified. It is acknowledged that since orthoses are visible interventions, worn by participants, it will be impossible to blind participants or personnel to group allocation. However, some blinding of outcome assessment is still possible. Any disagreements will be resolved through discussion, adjudicated if necessary by a third review author (AC), until a consensus is reached.
Measures of treatment effect
Risk ratios (RR) with 95% confidence intervals (CI) will be calculated for dichotomous outcomes and mean differences (MD) with 95% CI will calculated for continuous outcomes. When pooling continuous outcome data, standardised mean differences (SMD) will be calculated instead of mean differences where different scales or scores have been used.
Unit of analysis issues
For the majority of trials, we anticipate the unit of analysis will be the individual participant. However, unit of analysis issues may arise in studies that include participants with bilateral symptoms. Should these occur and no adjustments can be made, we will perform sensitivity analyses to explore the effects of including these data and trials in the review. We will be alert to other potential unit of analysis issues such as those relating to multiple observations for the same outcome. Thus, each follow-up period will be assessed separately in order to minimise the risks of unit of analysis error (Deeks 2011).
Dealing with missing data
Trialists will be contacted to provide missing data. Unless we can calculate missing standard deviations from standard errors, exact P values or 95% confidence intervals, we will not impute these or any other missing outcome data. If a paper only provides imputed data, the corresponding author will be contacted to request data on outcomes only from participants who were assessed. Where possible and appropriate, intention-to-treat analysis results will be used for all review analyses.
Assessment of heterogeneity
Study heterogeneity will be evaluated from an inspection of the characteristics of the included studies. Statistical heterogeneity will be assessed using Chi² and I² statistics, in addition to the visual inspection of the forest plots. The I² values will be interpreted as recommended by Deeks 2011. Thus, an I² value of 0% to 40% might 'not be important'; 30% to 60% may represent 'moderate' heterogeneity; 50% to 90% may represent 'substantial' heterogeneity; and 75% to 100% represents 'considerable' heterogeneity.
Assessment of reporting biases
If data for specific outcome measures are pooled from at least 10 trials, funnel plots will be generated to assess possible publication bias (Sterne 2011).
When there is heterogeneity between the studies in respect to the interventions, population or method of assessment, a narrative review of the results will be presented. Otherwise, where possible, results of comparable groups of trials will be pooled using both fixed-effect and random-effects models. The choice of the model to report will be guided by a careful consideration of the extent of heterogeneity and whether it can be explained, in addition to other factors such as the number and size of studies that are included. Ninety-five per cent confidence intervals will be used throughout. We will consider not pooling data where there is considerable heterogeneity (I² > 75%) that cannot be explained by the diversity of methodological or clinical features among the trials.
Subgroup analysis and investigation of heterogeneity
Planned subgroup analyses include:
- Different forms of orthoses: custom-made orthoses; prefabricated ('off-the-shelf') versions; bandages; and straps.
- Age (18 years or over versus under 18 years) and gender.
- Level of activity (participants who were professional athletes or in the military forces versus recreational athletes).
Factors such as age, gender, duration of PFPS symptoms prior to randomisation, type of intervention, length of follow-up, level of pre-injury activity, adjusted/unadjusted analyses will be considered during the interpretation of heterogeneity.
Sensitivity analyses will be conducted to explore different aspects of trial and review methodology. For example, planned sensitivity analyses include specifically assessing outcomes after the exclusion of trials at high risk of selection bias, and trials where the population is poorly defined. In addition, to address the potentially limitation of missing data, sensitivity analyses will be performed specifically assessing outcomes from studies which presented more than or equal to 90% of their originally randomised cohort at follow-up, as recommended by Higgins 2011b.
'Summary of findings' tables
Where there are sufficient data, we will summarise the results for the main comparisons described in Types of interventions in 'Summary of findings' tables. We shall use the GRADE approach to assess the quality of evidence related to each of the primary outcomes and, if possible, to at least the first two secondary outcomes listed in Types of outcome measures (Higgins 2011a; see 12.2).
We thank Michael Callaghan, Nigel Hanchard and Helen Handoll for their helpful feedback during the editorial review process, and Lindsey Elstub for her assistance in the preparation of this protocol. We also thank Joanne Elliott for her assistance in developing the search strategy.
Appendix 1. Search strategies
1 Patellofemoral Pain Syndrome/
2 exp Knee/ or Knee Injuries/ or Knee Joint/ or exp Patella/
3 Arthralgia/ or Pain/
4 2 and 3
5 anterior knee pain.tw.
7 ((patell$ or femoropatell$ or femoro-patell$ or retropatell$ or retro-patell$) adj2 (pain or syndrome or dysfunction or sublux or malalign$ or realign$)).tw.
8 ((lateral compression or lateral facet or lateral pressure or odd facet) adj syndrome).tw.
9 Chondromalacia Patellae/
10 ((chondromalac$ or chondropath$) adj2 (knee$1 or patell$ or femoropatell$ or femoro-patell$ or retropatell$ or retro-patell$)).tw.
12 1 or 4 or 11
13 exp Rehabilitation/
14 exp Physical Therapy Modalities/
15 Physical Therapy Specialty/
16 exp Orthotic Devices/
17 (brace$ or sleeve$ or strap$ or orthotic* or orthos#s or bandage$).tw.
19 (physiotherapy or physical therapy).tw.
22 (non-surg$ or nonsurg$ or non-operat$ or nonoperat$ or conserv$).tw.
24 12 and 23
25 Randomized controlled trial.pt.
26 Controlled clinical trial.pt.
29 Drug Therapy.fs.
34 exp Animals/ not Humans/
35 33 not 34
36 24 and 35
Contributions of authors
TS: Drafted the protocol; developed the search strategy; prepared, reviewed and agreed on the final protocol; acts as guarantor.
BD: Drafted the protocol; developed the search strategy; prepared, reviewed and agreed on the final protocol.
TM: Drafted the protocol; developed the search strategy; prepared, reviewed and agreed the final protocol.
AC: Drafted the protocol; prepared, reviewed and agreed on the final protocol.
Declarations of interest