Joint Position Sense in Individuals With Anterior Knee Pain
Conditions: Anterior Knee Pain Syndrome, Proprioceptive Disorders
Sponsor: University of Stellenbosch

 
 
Joint Position Sense in Individuals with Anterior Knee 
Pain 
 
ABSTRACT 
Introduction 
Anterior knee pain (AKP) commonly affects physically active as well as 
sedentary individuals and the aetiology remains unknown. Altered joint position 
sense (JPS) impacts accurate motor action and knee joint stability. It is unclear 
whether people with AKP have altered JPS. The aim of this study was to 
investigate the JPS of individuals with AKP. 
Methods 
A descriptive cross-sectional design was used to measure JPS in twenty-five 
participants with unilateral or bilateral AKP. The Vicon 3D motion analysis 
system was used to assess JPS by means of active joint position sense testing 
during single leg squat and active knee extension in sitting. Target angles were 
self-determined based on each participant’s capabilities. The absolute error 
(AE) was used as the main outcome measure. Impaired JPS was classified as 
an AE equal to or greater than five degrees.  
Results 
There were no significant differences in JPS when comparing the knees with 
AKP to the knees without AKP (p <0.05). However, a sub-group of participants 
with altered JPS was identified. There was a tendency towards a larger AE in 
the knees with AKP during active knee extension in sitting. 
Conclusion 

 
 
The results showed that JPS is not significantly more impaired in knees with 
AKP compared to knees without AKP. A sub-group was identified with altered 
JPS in knees with and without AKP. This finding could be due to compensatory 
gait patterns and the precision of the Vicon 3D motion analysis system. JPS 
should be assessed bilaterally in individuals with AKP. 
 
(Abstract: 248 words) 
 
 

 
 
 
INTRODUCTION 
Anterior knee pain (AKP) is a common disorder of the knee joint and affects 
young, physically active and sedentary individuals (Crossley et al 2016). AKP 
accounts for 25% to 40% of all knee problems presenting at sports medicine 
clinics; one in four of the active population is affected, leading to chronic knee 
pain among young adults(Crossley et al 2016; Coppack et al 2011; Dutton et al 
2016). AKP is prevalent among runners, particularly long-distance runners. AKP 
has a higher prevalence among active women, with an incidence two to three 
times more than that of men (Dutton et al 2016; Prins & van der Wurff 2009). 
AKP is characterised by anterior, peri-patellar or retro-patellar pain with an 
insidious onset and is exacerbated under conditions of increased patellofemoral 
joint stress (Dutton et al 2016; Nunes et al 2013). Aggravating activities include 
ascending or descending stairs, prolonged sitting, squatting, and running 
(Nunes et al 2013).The aetiology of AKP is unclear with a possible multi-
factorial nature and develops secondary to functional or structural mal-
alignment of the patellofemoral joint (Green et al 2014). Management of AKP 
remains challenging with 91% of patients with AKP reporting persistent 
symptoms after extended follow-up and medical management (Dutton et al 
2016).There is a therefore a need to understand the etiological pathways that 
may be causing the pain.  
Altered proprioception has been documented in patients with AKP (Akseki et al 
2008; Baker et al 2002; Cyrillo et al 2014; Guney et al 2016). Proprioception is 
“the use of joint position sense and joint motion sense to respond to stresses 

 
 
placed upon the body by alteration of posture and movement” (Norris 2011). 
Clinical symptoms of altered proprioception may include disturbed balance and 
clumsiness due to disturbed motor function and joint reflex stabilisation. Long-
term effects of altered proprioception among individuals with AKP may lead to 
recurrent and persistent pain with a secondary onset of joint osteoarthritis (Clark 
et al 2015; Röijezon et al 2015). 
Altered proprioception in individuals with AKP can be as a result of mechano-
receptor damage and may be associated with abnormal movement patterns 
and motor reactions (Clark et al 2015; Han et al 2016; Hillier et al 2015). These 
altered movement patterns and motor reactions include weak quadriceps 
muscles, altered timing of the VMO and altered tissue flexibility of the 
quadriceps and hamstring muscles (Kaya et al 2010; Lankhorst et al 2012). 
Altered motor reaction in AKP may be due to altered proprioceptive input from 
muscle spindles in skeletal muscles (Röijezon et al 2015). Muscle spindles in 
skeletal muscles are a type of mechano-receptor and a major source of 
proprioceptive feedback (Röijezon et al 2015). Another possible reason for 
altered proprioception in a population with AKP could be due to small nerve 
damage in the lateral retinaculum of the patella (Sanchis-Alfonso & Rosello-
Sastre 2003).This nerve damage in the lateral retinaculum can be due to the 
maltracking of the PFJ (Sanchis-Alfonso & Rosello-Sastre, 2003). It is unclear 
whether altered proprioception could be a risk factor leading to AKP or could 
contribute to the chronicity of the condition. 
The ability to accurately sense joint position (JPS) is essential for an individual 
to respond to stresses placed upon the body(Smith et al 2013). JPS testing can 

 
 
be tested under active (biasing joint mechanoreceptors) or passive (stimulating 
joint and muscle tendon mechanoreceptors) conditions (Roijenzon et al 2015). 
JPSis the ability of an individual to accurately reproduce a target angle (Selfe et 
al 2006; Baker et al 2002). The most common clinical metric use to assess JPS 
is absolute error (AE). AE refers to the difference between the target angles and 
the response angle (Orgard 2011; Han et al 2015; Hillier et al 2015; Röijezon et 
al 2015). 
There is limited research investigating JPS in individuals with AKP (Yosmaoglu 
et al 2013).Previous studies in this field reported no significant differences in 
JPS between individuals with and without AKP (Bennel et al 2005; Naseri et al 
2012; Yosmaoglu et al 2016).Contrary to these findings it has been reported 
that JPS was significantly affected in an AKP population compared to 
controls(Akseki et al 2008; Baker et al 2002; Cyrillo et al 2014; Guney et al 
2016). 
Although all of these studies measured JPS, different methods for measuring 
JPS were used including (1) image recorded where photography is used to 
assess knee joint angles (Naseri et al 2012; Baker et al 2002); (2) electro-
goniometry with knee angular error (Akseki et al 2008; Cyrillo et al 2014); (3) 
dynamometry (Guney et al 2016) and (4) a functional loaded squat system 
(Yosmaoglu et al2013). Three studies measured NWB JPS only (Akseki et 
al2008; Yosmaoglu et al2013, Guney et al 2016), whereas the other studies 
combine WB and NWB. WB positions have been shown to be more accurate, 
however, NWB knee JPS had the greatest potential for isolating the 
proprioceptive status of the knee joint only (Stillman & McMeeken 2001). There 

 
 
were also differences in the study samples. The studies that found no 
significant differences used very specific populations included pain-free 
subjects with induced AKP (Bennel et al 2005), athletes (Naseri 2012) and 
women (Yosmaoglu et al 2013).  
The variation in methodology could also be due to the lack of a gold standard 
test to assess JPS. Furthermore, the tests used in previous studies have poor 
clinical applicability and are poorly evaluated and reported on by the respective 
authors (Guney et al 2016). Current studies use 1D and 2D systems only. It is 
possible that these methods are not sensitive enough to detect small changes 
in AE. The VICON 3D movement analysis system is considered the gold 
standard objective measure for 3D postural analysis (Brink et al 2013). 
An additional problem with the current evidence is the lack of clear classification 
system of what constitutes ‘good’ or ‘poor’ JPS. The current evidence on 
subjects with AKP only compares differences between AKP and control groups 
with no clear interpretation of what the values mean. Relph and Callaghan 
(2016) assessed 116 healthy, pain free participants between 18-82 years old. 
They assessed the normative JPS AE values into flexion and extension. The 
mean AE values ranged between 3.1-3.9 degrees for flexion and 2.5- 3.9 for 
extension. The minimal detectable difference for JPS has been reported to 
range from 1.23-2.14 degrees in AE scores (Relph & Harrington, 2015). Clark et 
al (2016) reported that the AE scores ranged between 3.18 and 5.97 degrees in 
healthy pain-free adults. It is unknown how much of a difference in AE is 
needed to increase the risk of injury. However, based on these precious studies 

 
 
we used an AE greater than five degrees as an indication of poor JPS for the 
purpose of this study.  
More research is needed to establish if individuals with AKP present with 
altered knee JPS as this could potentially lead to altered movement patterns 
and ongoing pain. Clinicians need to know whether to address JPS in 
rehabilitation when treating patients with AKP. The aim of this study, therefore, 
is to determine if JPS is altered in individuals with AKP. This is the first study 
that uses the Vicon 3D motion analysis device the accurately measure JPS 
during weightbearing in an AKP population.  
 
METHODS 
Research Design 
CAF Human motion analysis Unit, Faculty of Medicine and Health Sciences, 
Stellenbosch University. Ethical approval was obtained from the Health 
Research Ethics Committee of Stellenbosch University under reference number 
S16/10/197. This study was conducted as part of a master’s thesis project 
(Rhode 2018). 
Participants 
The target population consisted of 25 males and females between the ages of 
14 and 40 years. This was calculated using a pragmatic approach and based 
on previous studies (Akseki et al 2008; Baker et al 2002; Cyrillo et al 2014; 
Guney et al 2016). Informed consent was obtained and completed by all 
participants prior to the study procedure. Where participants were under the age 

 
 
of 18 years an assent form was obtained as well as informed consent from the 
parents/guardians.  
Inclusion and Exclusion Criteria 
Inclusion criteria 
Participants who adhered to the criteria listed below were considered for 
inclusion. Individuals aged between 14 and 40 years, with an insidious onset of 
clinical signs and symptoms of AKP. Participants were included if symptoms 
were provoked by prolonged sitting, squatting, stair-climbing and/or running. 
Participants who complied with the AKP screening tool and the diagnostic 
checklist (Leibbrandt & Louw 2017) were considered for inclusion. Screening 
was done by the primary researcher (CR) who had been trained to use the 
screening tool by another researcher with experience in treating AKP (DL). 
Participants with unilateral and bilateral AKP were considered for inclusion. In 
cases where both knees were affected with AKP, both knees were tested for 
altered JPS and compared to the knees without AKP.  
Exclusion criteria   
Participants were excluded if AKP had resulted from a traumatic event such as 
a motor vehicle accident, if they had previous knee surgery or injuries, if there 
was clinical evidence of other knee pathologies, if they were experiencing any 
other lower extremity injuries. Participants needed to comply with the initial AKP 
screening tool and diagnostic checklist (Leibbrandt & Louw 2017) developed 
specifically for this study in order to be included.  
Sampling and Recruitment 

 
 
Sample recruitment was aimed to attract individuals with AKP from different 
socio-economic backgrounds, sporting codes and areas. Letters of invitation 
were sent to various universities, sports clinics, physiotherapy practices and 
sporting clubs.  
Study Procedure  
Measurement Tools 
Vicon 3D motion analysis system 
The eight-camera Vicon T-20-series motion analysis system (Vicon Motion 
Systems Ltd., Oxford, UK) with Nexus 1.7 software was used to assess joint 
position sense (JPS). The Vicon has demonstrated high accuracy and reliability 
and has been shown to have less than a 1.5-degree error (Ehara et al 1997; 
Richards 1999). Retro-reflective markers with a diameter of 9.5mm were used. 
Dynamic calibration was performed according to standard laboratory protocol, 
and the Vicon T-wand was placed on a 3D Bertec force plate (Bertec 
Corporation Ltd.), which is synchronized with the Vicon motion analysis system. 
H-Frame 
An H-frame was constructed based on a study by Clark et al (2016). The 
function of the H-frame was that of a range of motion (ROM) guide when 
establishing the target angle (TA) for participants during the test trial. The H-
frame was positioned so that the rubber band (cross bar) makes contact with 
the distal part of the patella during single leg squat (SLS) and that the crossbar 
touches the skin overlying the anterior ankle joint line during active knee 
extension (AKE). The H-frame was removed during the test procedure. 

 
 
Kujala/anterior knee pain scale (AKPS) questionnaire  
The AKPS is a 13-item knee functional questionnaire. This scale is scored out 
of 100, with a higher score indicating less disability. The AKPS demonstrated 
high reliability and responsiveness in a population of patients with AKP (Watson 
et al  2005; Crossley et al 2004).  
Visual analogue pain scale (VAS) 
This VAS scale is a well-known outcome measure to evaluate levels/intensity of 
pain (Crossley et al 2016). The VAS is scored from 0 (no pain) to 10 (maximum 
pain). The VAS demonstrates good reliability and responsiveness among a 
population of patients with AKP (Bennel et al 2000; Crossley et al 2004; Green 
et al 2014).  
Lower extremity functional scale (LEFS) questionnaire 
The LEFS consists of 20 items that measure the ability to perform various 
functional activities and activities of daily life. The LEFS is scored out of a 
maximum score of 80. The LEFS demonstrates high reliability and 
responsiveness in the population of patients with AKP (Crossley et al 2004; 
Watson et al 2005). 
Criteria for positive and negative knee joint position sense 
The main outcome measurements for knee JPS testing was absolute error 
(AE).  AE refers to the difference between the test or target angle and the 
reproduced angle. Absolute error represents accuracy without directional bias. 
For the purpose of this study, abnormal JPS was defined as an AE equal or 
greater than five degrees. This criterion was based on published research by 

 
 
Relph and Callaghan (2015; 2016) and Clark et al (2016) using healthy pain 
free participants. The mean AE from five trails for each test was used for 
statistical 
analysis 
(Selfe 
et 
al 
2006). 
 
 
Testing Procedures 
Initial screening 
To verify that participants met the inclusion criteria they completed a screening 
questionnaire via email. Prior to JPS testing, participants completed the AKP 
scale questionnaire (AKPS) and the LEFS questionnaire. A data collection form 
was used to collect participant personal details and variables including age, 
gender, body length, episodes and duration of AKP, area of symptoms, type of 
treatment received for AKP and sport participation. A flowchart of the study 
procedure can be seen in Figure 1.  
PLACE FIGURE 1 HERE  
Physical examination and diagnosis 
The diagnostic checklist was completed, and the physical examination was 
performed to confirm a diagnosis of AKP and to exclude other knee pathologies 
prior to testing. The physical examination (P/E) was conducted by the primary  
researcher (CR), who is an experienced physiotherapist. Additionally, 
anthropometrics (weight, BMI, leg length) were measured for each participant. 
Data were captured as part of participant demographics to describe this 
population group/participants. 

 
 
Preparation for Vicon testing 
Participants were dressed in short pants, were barefoot, with clean shaven legs 
with no lotion on legs to ensure effective marker placement. Thirty retro-
reflective markers were placed on bony landmarks according to lower limb Plug-
in Gait model (Clark et al 2016). Additional pelvic markers, a sacral wand, two 
extra shin markers and extra anterior and posterior thigh markers where added, 
to ensure joint position sense accuracy. The primary researcher (CR) performed 
the marker placement assisted by a research assistant. Reflective markers 
were placed in the standing position in preparation for SLS and re-applied with 
the participant in the seated position to ensure accurate positioning of markers 
placements for active knee extension. A static and dynamic calibration were 
performed in both test positions.  
Pain measurement 
During the test trials the participants were asked to verbally indicate the severity 
of their anterior knee pain using the VAS pain scale. Pain severity was 
measured at the start and end of proprioceptive testing.  
Proprioceptive Testing 
All participants were familiarized with the proprioceptive test procedure by 
means of explanation, demonstration and a practice opportunity. The 
participants were asked to resume the test position i.e. (i) standing or (ii) sitting. 
The target angle was determined by each participant according to his/her 
capabilities and comfort level, i.e. the target angle was unique to each 
participant.  

 
 
Single leg squat (SLS) 
Starting position 
For the SLS the participant supported one hands on a chair for balance. The 
participant was standing on the tested leg, while the other leg was slightly 
flexed at the hip and knee in a position that was comfortable for the participant 
(Figure 2).  
Instructions to participant 
The participant was asked to do a SLS and stop in the mid-range. The 
participant was asked to briefly hold this mid-range angle to position the H-
frame indicating this angle as the target angle (TA). 
Test trial 
The participant was cued to squat down till they felt the cross bar of the H-
frame. The participant was instructed to hold the SLS for five seconds to 
establish and familiarize themselves with the target angle (TA). The test trial 
was repeated five times. 
Test procedure 
The participant was blindfolded, and the H-frame was removed. The participant 
was instructed to perform a SLS, and to indicate when they had reached the TA 
by shouting STOP. This position indicated the relative error (RE) and was 
maintained for five seconds to record the data. Testing was repeated five times. 
This number of repetitions has been recommended for JPS testing in previous 
research (Selfe et al 2006). SLS was repeated on the knees without AKP for 
comparison.  
PLACE FIGURE 2 HERE  

 
 
Sitting: active knee extension (AKE) 
Starting position 
The participant was seated on an 800mm high bar stool, with both feet 
supported. Each participant was positioned with the popliteal fossa 
approximately 5cm from the edge of the chair. The participant’s arms were 
crossed over their chests comfortably to avoid obstruction of the pelvic markers 
(See figure 3).  
Instructions to participants 
The participant actively extended the knee through the range of 90 knee flexion 
to 0 knee extension; thereafter they had to stop in the mid-range position. The 
participant was asked to briefly hold this mid-range angle to position the H-
frame indicating this position as the TA. The participant was verbally cued to 
resume the starting position.  
Test trial 
The participant actively extended the knee from the starting position of 90knee 
flexion to the TA. The participants were verbally cued to hold this position for 
five seconds to establish the TA. Thereafter the participant was asked to return 
to the starting position of the knee in 90flexion. The test trail was repeated five 
times.  
Testing 
The H-frame was removed at the commencement of AKE testing. The 
participant was asked to repeat AKE, indicating when the TA had been 
reached, by shouting STOP. This position indicated the relative error (RE) and 

 
 
the participants maintained this position for five seconds. Testing was repeated 
five times. The AKE was repeated on the knees without AKP for comparison.  
PLACE FIGURE 3 HERE  
Statistical Analyses  
All descriptive data (demographic information, functional and pain scales) were 
analyzed using descriptive statistics to indicate central tendencies in data 
(means and standard deviations). A non-pragmatic test approach was adopted 
by illustrating the ranges. Data was captured through the Vicon Nexus 3D 
motion analyses system. Chi-square calculations was performed to determine a 
significant difference in JPS between the knees with AKP and the knees without 
AKP during single leg stance and active knee extension.   
 
 

 
 
 
RESULTS 
Participant demographics 
A total of 25 participants complied with the inclusion criteria (Table 1); with the 
majority being female (n=22).  The participants had a mean age of 27.8 years 
and a mean BMI of 28.2 kg/m2 (range of 20.9- 45.7kg/m). Twelve (52%) of the 
participants reported having AKP symptoms in both knees and ten (40%) 
participants reported their right knee as most affected. Nineteen (76%) of the 25 
participants reported being physically active and six (24%) were sedentary. The 
participants’ mean usual pain level according to the VAS was 4.5/10. 
PLACE TABLE 1 HERE  
 
Symptom presentation 
Participants’ duration of symptoms ranged from two months to 11 years with a 
mean duration of 28.4 months (Table 2). Participant’s area of symptoms was 
predominantly in the front of the patella (n=10;40%) or in front and just below 
the patella (n=10;40%) and five participants (20%) reported their area of 
symptoms to be behind the patella. The most frequently reported aggravating 
activities were squatting (n=19;76%), prolonged sitting (n=10;40%) and going 
up stairs (n=11;44%).  
Participant activity level 
The participants who stayed active through physical exercise reported a mean 
training frequency of 2.8 times per week and training ranged from zero to six 

 
 
times per week. The participants’ sporting activities were predominantly gym 
(n=12;48%) and running (n=11; 40%), with two (8%) participants reporting 
being dancers. Fourteen (56%) of the participants reported not seeking any 
medical treatment for their AKP symptoms, whereas nine (36%) reported using 
NSAIDs as needed. Fifteen (60%) of the participants were able to do all 
activities of daily living (ADL); where as 36% of participants stopped all physical 
activity due to the severity and intensity of the AKP.  
PLACE TABLE 2 HERE  
Outcome measures 
The participants AKPS ranged from 52 to 92 with an average of 72 out of 100 
points. A score of 70-100 represents moderate disability (Singer B & Singer K 
2009). The LEFS ranged from 31 to 77 with an average of 58 out of 80 points 
indicating moderate functional impairment. Participants reported that pain levels 
during proprioceptive testing procedure ranged from zero to 9/10 on the VAS 
scale with a mean pain level of 4.5 out of 10.  
Physical examination 
The aggravating functional activities that reproduced the participants known 
AKP symptoms were predominantly squats (n=25; 100%), going both up and 
down stairs (n=5; 20%) and going down stairs respectively (n=4; 16%).During 
the physical examination of the PFJ, the passive accessory movements easily 
reproduced the patients’ symptoms. A positive patellar compression test was 
reported by 22 (88%) of participants. Other PFJ accessory movements were 
also positive in 11 (44%) of the participants and palpation of the patella border 
reproduced six (24%) of the participants’ pain. 

 
 
JPS results 
JPS testing was performed for both knees of every participant (n=25); therefore 
50 knees were assessed. Thirty-seven of the fifty knees were classified as 
affected with AKP (knees with AKP) and thirteen were classified as unaffected 
with no reported symptoms of AKP (knees without AKP). The proprioceptive 
results for the knees with AKP and the knees without AKP are presented in 
Table 3. 
PLACE TABLE 3 HERE  
SLS, comparing knees with AKP and knees without AKP 
The mean target angle (TA) of the knees with AKP (n=37) was 39.5 degrees 
compared to 44.4 degrees in the knees without AKP (n=13). The knees with 
AKP had a bigger variation in the TA range compared to the knees without 
AKP. When comparing the absolute errors (AE) the knees with AKP had a 
smaller AE compared to the knees without AKP, with a greater variation in the 
range of the AE of the two groups. The relative error (RE) was smaller in the 
knees with AKP (1.4 degrees) with a greater range (-12.1 to 4.5) compared to 
the knees without AKP (-10.8 to 3.8). There was no difference between the AE 
or the RE of the knees with AKP compared to the knees without AKP during 
JPS testing in single leg squat.  
 
Sitting: AKE, comparing knees with AKP to knees without AKP 
The mean TA of the knees with AKP (n=36) was 31.7 degrees compared to 
33.5 degrees in the knees without AKP. The AE was the same (AE=4.2 
degrees) for both the knees with AKP and the knees without AKP. However, 

 
 
there was a difference when comparing the standard deviation and the range of 
the AE between the two groups. The group with AKP displayed greater 
variability compared to the group without AKP. The RE for knees with AKP was 
-1.8 degrees compared to 1.2 degrees in the knees without AKP. When 
comparing the RE, the knees with AKP demonstrated a greater variation in 
range (-16–8.7) compared to the knees without AKP (-7.2 – 6.1).  
Altered JPS in both the knees with AKP and the knees without AKP (n=50) 
A total of thirty-seven knees (37/50) presented with AKP (Table 4). During SLS 
10/37 (27%) of the knees with AKP presented with altered JPS with an AE 
equal or greater than five degrees. The mean AE of the ten knees with AKP and 
altered JPS was 7.4 degrees with a range of five to twelve degrees. Twenty-
seven (73%) of the knees with AKP had an AE of less than five degrees, with a 
mean AE of 2.6 degrees (range: 0.6 to 4.5). 
During AKE 10/36 (28%) of the knees with AKP presented with altered JPS with 
an AE equal or greater than five degrees. The mean AE of the ten knees with 
AKP and altered JPS was 8.3 degrees and ranged between five and 16 
degrees, compared to a mean AE of 2.6 degrees and a range of 0.9 to 4.6 
degrees for the 26 knees with AKP and good JPS. 
PLACE TABLE 4 HERE  
Thirteen of the fifty knees (26%) had no symptoms of AKP (knees without AKP). 
During SLS six of the thirteen (46%) knees without AKP had altered JPS with 
an AE equal or greater than five degrees. The mean AE during SLS for the 
knees without AKP was 8.3 degrees, with a range of 5.4 to 10.8 degrees. The 

 
 
mean AE of the knees without AKP during AKE, was 2.6 degrees with a range 
of 1.8 to 3.9 degrees.  During AKE, four of the thirteen (30%) knees without 
AKP presented with altered JPS with an AE equal or greater than five degrees. 
The mean AE was 5.9 degrees with a range of 5.2 to 7.2 degrees. The 
remaining nine participants in this group had a mean AE of 3.5 degrees and a 
range of 1.6 to 4.9 degrees indicating unaffected JPS. 
The Chi-square statistic was 1.61 between the knees with AKP and the knees 
without AKP during SLS, with a p-value was 0.20 indicating no significant 
difference (p > 0.05), whereas the Chi-square statistic was 0.04 between the 
knees with AKP and the knees without AKP during AKE with a p-value was 
0.08, indicating no significant difference (p > 0.05). 
PLACE TABLE 5 HERE  
 
 
 

 
 
DISCUSSION 
The main finding of this study is that there were no significant differences in 
knee JPS when comparing the knees with AKP to those without AKP. For both 
these groups the mean AE showed no comparative difference in either the SLS 
and AKE positions. However, a subgroup of subjects with impaired JPS 
bilaterally was identified. Approximately a third of the study participants were in 
this sub-group. Research into AKP and JPS has yielded inconsistent findings. 
Some studies have concurred with our findings of none significant JPS 
differences between knees with and without AKP (Bennel et al 2005; Naseri et 
al 2012; Yosmaoglu et al 2013). These studies also used JPS to evaluate knee 
proprioception and calculated the AE to express JPS. Contrary, a number of 
published papers have stated that JPS is affected more in people with AKP 
compared to individuals without AKP (Akseki et al 2008; Baker et al 2002; 
Cyrillo et al 2014; Guney et al 2016). These contradictory findings could be as a 
result of differences in study methodology and participant characteristics.  
Later, an interesting observation was that a number of knees without AKP also 
had altered JPS according to the classification criteria (Callaghan et al., 2002). 
Similar results have been reported when comparing JPS in individuals with AKP 
compared to healthy controls (Baker et al 2002; Cyrillo et al 2014). These 
authors found JPS to be altered in the knees with AKP as well as the knees 
without AKP. The interpretation of altered JPS in the knees without AKP is 
unclear but could be due to compensatory mechanisms during gait in people 
with AKP (Barton et al 2009). Patients with AKP may develop a quadriceps 

 
 
avoidance gait pattern to decrease PFJ reaction forces and to avoid pain 
(Sanchis-Alfonso et al 2016). 
It must be considered that classification of abnormal JPS has not been used in 
a population affected with AKP. The group of knees without AKP were much 
less than the knees with AKP making if very difficult to compare the 
proprioceptive findings. Inter-subject comparisons for each participant’s 
proprioceptive outcomes were not compared and should be considered in future 
studies.  A small percentage of the knees with AKP and the knees without AKP 
had an AE greater than five degrees. These findings cannot be generalised to 
the rest of the population due to the small sample group. 
In this study participants with unilateral and bilateral AKP were included, which 
differs from previous studies that used control groups without AKP for 
comparison. AKP symptoms in this study population were not restricted to just 
one knee, as more than half the individuals reported both knees being 
symptomatic. The literature also makes note of this as previous studies in this 
field have indicated that AKP can be present in both knees (Kurt et al 2016). If 
the pathological and normal knees are affected this could indicate that JPS 
should be considered in the aetiology in this subgroup (Akseki et al 2008). 
Previous studies with similar findings included an athletic population (Naseri et 
al 2012),females diagnosed with PFP (Yosmaoglu et al 2013) and healthy 
participants with induced AKP (Bennel et al 2005). In athletes (Naseri et al 
2012), it seems that AKP does not affect the knee JPS, compared to pain-free 
controls. The lack of deficiency in patients could possibly be attributed to their 
severity of knee pathology, pain intensity and their physical activity level. In the 

 
 
present study, the patients were athletes with moderate pain in their knee joints. 
Whether their functional state enhanced their proprioceptive (JPS) ability and 
whether their severity of knee pathology and pain intensity was such that their 
proprioceptive abilities were not significantly affected are unclear. Athletes with 
a higher functional level and moderate pain may not present with proprioceptive 
deficits. In females (Yosmaoglu et al 2013), active reproduction of joint position 
did not differ between AKP and control groups.  The authors also suggested 
that subject groups may have differed in terms of pain or strength levels. 
In the current study participants were included irrespective of their sport 
participation or activity levels, whereas previous studies included athletes or 
restricted the population to only females diagnosed with AKP. The literature 
highlights that AKP is common among active individuals (more so runners) and 
has a higher incidence in females (Neal et al 2016; Prins & van der Wurff 
2009).The current study population is reflective of these findings, with females 
constituting the majority of the study population, two-thirds were active 
individuals and 44% where runners. This study however highlights that AKP 
does not only affect the athletic population but can affect sedentary individuals 
as well (Crossley et al 2016).Seventy-six percent of the participants were 
physically active and activity levels ranged up to six times per week with an 
average activity level of 2.8 times per week. The athletic abilities and higher 
levels of motor function could account for proprioceptive feedback from adjacent 
joints and muscles (Naseri et al 2012; Smith et al 2013).The severity of the AKP 
pathology, participants’ pain levels and activity levels are thought to have 
influenced proprioceptive function in these studies. The pain levels of the 

 
 
population group in the current study ranged between zero to nine out of ten 
with a mean pain level of (4.5/10). It can be debated that pain severity levels 
needed to be higher than moderate to influence proprioceptive abilities (Naseri 
et al 2012). 
One study (Bennel et al 2005) investigated the effect of induced AKP on a 
healthy population to determine if the pain itself influenced JPS. The findings 
were that Knee JPS is reduced by an attention-demanding task but not by 
experimentally induced pain. Therefore, JPS dysfunction may occur before pain 
or be a risk factor in a subgroup rather than as a result of pain. If this is the 
case, then resolution of pain is unlikely to lead to improvements in JPS, and it 
would need to be addressed in treatment. 
The current study defined abnormal knee JPS as an AE equal or greater than 5 
degrees. This criterion was based on a study by Callaghan (2002), who tested 
the criterion on healthy participants. The definition of the normative criterion for 
abnormal JPS in this study was necessitated due to the lack of a defined 
normative criterion in participants with AKP(Callaghan 2011). 
In the current study JPS was tested in both a weight bearing (SLS) and non-
weightbearing position (AKE). Previous studies predominantly tested JPS in 
only a non-weight bearing position (Akseki et al 2008; Bennel et al 2005; Cyrillo 
et al 2014). The Biodex 360 was used to measure knee JPS in more recent 
studies. The Biodex 360 is considered a reliable measurement tool to evaluate 
knee JPS, however it can only account for a non-weight bearing test position.  
Weightbearing test positions are more likely to be relevant in an AKP population 
as this is when patients typically experience pain. However, JPS in weight 

 
 
bearing positions need to be measured accurately and reliably. In the current 
study Vicon 3D motion analyses allowed for testing knee JPS in both standing 
and sitting. The Vicon 3D motion analyses system is regarded as the gold 
standard in motion analyses (Ehara et al 1997; Richards 1999).The current 
study is the first study to make use of the Vicon 3D motion analyses to assess 
knee JPS in an AKP population, which allows for a weightbearing assessment 
of JPS. Stillman and McMeeken (2001), compared JPS testing during a 
weightbearing and non-weight bearing test position. They found WB testing to 
be more reliable and accurate for JPS compared to NWB test procedures. 
However, NWB testing had a greater potential to isolate the proprioceptive 
status of the knee joint only. Therefore, it is recommended to use a combination 
of both methods.  
Limitations 
There is still limited research on investigating JPS changes in individuals with 
AKP, and conflicting results remain a cause of concern. The use of larger 
sample groups and being able to match cases to healthy controls with 
unaffected knees should be addressed in future studies. In this study only JPS 
testing was done, which is only one aspect of proprioceptive testing. 
The best test procedure still needs to be described to assess JPS as it remains 
challenging to conclude findings due to variation in testing methods and 
measurement tools. There may be a sub-group of patients who have both AKP 
and poor JPS (Callaghan et al 2011); which is cause and which is effect, 
remains uncertain, until prospective studies are undertaken. 

 
 
In the current study we did not exclude participants with a high BMI. Excess soft 
tissue influences the reliability of the motion analysis as it can cause movement 
of the markers and wands during motion capture procedures. Another possible 
factor is that the extra weight itself could have been a contributing factor in the 
development and chronicity of the knee symptoms due to the increased loading 
of the knee joint. Future studies should consider excluding obese participants 
with a BMI of more than 30 to control for this.  
The age range of the included participants was between 14 and 40. However, 
the current study did not compare the JPS of the younger adolescent 
participants to adult participants. Future studies should investigate the 
differences between these age groups with regards to JPS.  
It has also been suggested that an increased  Q-angle heightens the risk of 
developing AKP (Emami et al 2007). Nakagawa et al (2015) proposed that an 
increased dynamic Q angle during sls may indicate an inability of the individual 
to stabilize the lower limb in the frontal plane. An increase dynamic Q angle 
could result in increased forces on the lateral patella facets and abnormal 
stresses on trochlear groove during loading and subsequently knee pain. 
Frontal plane mechanics were not measured in this study and therefore It is 
therefore unclear how abnormal biomechanics correlate with JPS findings. This 
should eb addressed in future research.  
 
CONCLUSION 
This study investigated JPS in individuals with AKP. The findings showed that in 
an AKP population, JPS is not significantly more impaired in knees with AKP 
compared to knees without AKP during active reproduction proprioceptive 

 
 
testing. The use of the Vicon 3D motion analysis system added to the 
measurement precision. The findings in this study suggest that a subgroup of 
individuals with altered JPS may exist in an AKP population, however it is 
unclear whether altered JPS is a cause or effect of pain. Longitudinal research 
needed to establish how altered JPS relates to the pain experienced.  
 
CLINICAL RELEVANCE 
• A subgroup of individuals with altered JPS exists in a population with 
AKP  
• When assessing individuals with AKP knee JPS should be assessed 
bilaterally and in both weightbearing and non-weightbearing positions 
• Proprioceptive rehabilitation should be considered in the individualised 
management of population groups with AKP when deficits occur 
 
 
(Total word count: 5819 words)  
 
 
 

 
 
ACKNOWLEGEMENTS  
The authors wish to acknowledge that this work is based on the research 
supported in part by the National Research Foundation (NRF) of South Africa. 
We would also like to express gratitude towards Stellenbosch University for the 
use of their facilities.  
 
 
 

 
 
 
 
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