ReviewMethods to assess patellofemoral joint stress: A systematic review
Introduction
Patellar malalignment is a common finding in people with patellofemoral joint (PFJ) pain [1] and PFJ osteoarthritis [2], the two main PFJ dysfunctions. The association between patellar malalignment and the resultant force from quadriceps muscle and patellar tendon actions [3] may contribute to the progression of PFJ dysfunctions. Due to changes on PFJ contact area from the malalignment, PFJ reaction force may not be dissipated adequately [4]. Consequently, interferences on the relationship between patellar forces and patellar alignment may be related to pain and morphological changes such as osteophytes and loss of cartilage [2,5].
The relationship between patellar forces and contact area has been commonly investigated by measuring the stress these forces can create in the PFJ [[6], [7], [8], [9], [10]]. For PFJ stress calculations, the force imposed in the patella is divided by the contact area between the patella and femur [6,8,11,12]. PFJ stress measure has been reported during different activities such as running [13,14] and squatting [15,16]; also in different populations, such as those with PFJ pain [6] and those with PFJ osteoarthritis [17].
As PFJ stress cannot be directly measured in vivo, studies present data on PFJ stress based on mathematical models currently available in the literature [6,18,19]. The majority of the studies underwent the steps below described and presented in Fig. 1 in order to calculate PFJ stress:
1st step: kinematic and kinetic data are obtained from participants during some activity, usually with the use of cameras and force platforms. The knee flexion angle and knee extensor moment are measured and used in the PFJ stress mathematical model. Knee angles and moments are calculated indirectly through biomechanical models [20]. Although these measurements are considered reliable, there is the potential of miscalculating them [20]. In the sagittal plane knee angle calculations could have approximately five degrees of error during gait measurement [21] and knee extensor moment could have approximately 10 Nm of error during vertical drop jumps [22].
2nd step: quadriceps muscle effective lever arm (Leff) is calculated. This is a step to estimate quadriceps force. Studies commonly use data previously published to develop a formula in which knee flexion angle is the dependent variable [6,18]. Data for the development of the formulas is based on measures from images of the knee in the sagittal plane, from radiography or magnetic resonance imaging (MRI), and its accuracy is uncertain [9,23].
3rd step: quadriceps muscle force is calculated. This is a step to obtain PFJ reaction force. Knee extensor moment obtained during an activity is divided by the calculated Leff. This step is required to isolate the force generated by the quadriceps muscle [24].
4th step: coefficient k is calculated. This is also a step for the PFJ reaction force calculation. Coefficient k is a constant that defines the relation between quadriceps force and PFJ reaction force as a function of knee flexion angle [9]. Studies usually use data previously published to develop a formula in which knee flexion angle is the dependent variable [25,26]. However it is difficult to know whether the theoretical approach used in some of the studies are likely to generate significant error in the estimates [9].
5th step: PFJ reaction force is calculated. The calculated quadriceps muscle force is multiplied by the calculated coefficient k. The estimated error in this measure is approximately 50N [27].
6th step: calculation of PFJ contact area. Most studies used previously published data to develop a formula in which knee flexion angle is the dependent variable [18,28]. Methods were developed based on the contact area of the PFJ of cadavers, healthy people and people with knee injuries [29,30]. The estimated error for PFJ contact area, measured by MRI, is approximately 40 mm2 [31].
7th step: final step where PFJ stress is calculated by dividing PFJ reaction force by PFJ contact area.
Interestingly, although the majority of studies have reported to follow these steps, there are different mathematical models to reach values of PFJ stress. Some studies used a wider range of data from their participants as opposed to using data from previous studies as described above. These studies collected data via MRI and used the new collected data from their own participants to calculate PFJ contact area, Leff and coefficient k [19,23]. The assumption of cocontraction of knee flexors and extensors is another difference among mathematical models to calculate PFJ stress [32,33].
Given the complexity of the methods and potential error associated to each method, it is difficult to compare results from studies that used different methods. This was demonstrated in the study by Kernozek et al. [16], where two methods to estimate quadriceps muscle force were compared and results showed a significant difference in PFJ stress of approximately 7 MPa [16]. For that reason, slight differences in the used methods for PFJ stress calculation could potentially lead to misinterpretation of the findings. Studies that used PFJ stress calculation might have been performed without the required attention which compromises the findings and potentially misleads readers who are interested in the PFJ stress field. It also highlights the importance of using consistent methods to calculate PFJ stress. Furthermore, some statements and hypotheses on PFJ dysfunctions, based on PFJ stress, indicate that some clinicians and researchers may be unfamiliar with the available methods used to calculate PFJ stress. For example, some studies suggest that the presence of excessive dynamic knee valgus during activities could increase the PFJ stress [34,35]. This statement may be true; however, no factor related to frontal plane is applied in the methods to calculate PFJ stress and therefore such statement is in disagreement with the present literature. Therefore, the aim of the current study was to systematically review the mathematical methods used in the literature to calculate PFJ stress and to potentially identify the best method to calculate PFJ stress. We also aimed at addressing the complexity of the methods by highlighting the differences among the methods.
Section snippets
Methods
This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations [36].
Study selection
A total of 12,670 titles were retrieved from the searches. In the initial search in five databases, a total of 9667 titles were found, of which 42 papers met the eligibility criteria (Supplementary material 2 – Flow diagram). After inclusion of the references of included papers and citation checking 3003 titles were further screened and 11 more papers met the eligibility criteria. These studies were not part of the databases searched in the current study or were in press.
Of the 53 included
Discussion
After analyzing the PFJ stress results reported by the included studies, a large variability was noticed. For example, studies with similar activities and population presented PFJ stress differences larger than 15 MPa for the running activity in healthy people. These results are alarming, because the variability noticed in the present review is greater than the difference in PFJ stress presented by studies comparing healthy and affected populations [6,17]. Brechter and Powers [6] reported that
Conclusion
PFJ stress calculation used by the majority of the studies has many indirect calculations; however methods with more data from participants might be preferred as direct measures are more likely to minimize the potential errors in the indirect calculations. When direct measures are not possible, based on the studies analyzed in the current systematic review, the model that seems to be the most appropriated is:
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Quadriceps Muscle Effective Lever Arm (Leff) = 8.0E − 05x3–0.013x2 + 0.28x + 0.046;
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Conflicts of interest
The authors declare no conflict of interest.
Acknowledgments
The authors would like to acknowledge the São Paulo Research Foundation – FAPESP (process 2015/01704-7 and 2016/09438-7).
References (95)
- et al.
Tibiofemoral and patellofemoral mechanics are altered at small knee flexion angles in people with patellofemoral pain
J. Sci. Med. Sport
(2013) - et al.
A mathematical model of the patellofemoral joint
J. Biomech.
(1986) - et al.
Patellofemoral joint kinetics during squatting in collegiate women athletes
Clin. Biomech.
(2001) - et al.
Comparison of two methods of determining patellofemoral joint stress during dynamic activities
Gait Posture
(2015) - et al.
Individuals with isolated patellofemoral joint osteoarthritis exhibit higher mechanical loading at the knee during the second half of the stance phase
Clin. Biomech.
(2015) - et al.
The influence of reduced hamstring length on patellofemoral joint stress during squatting in healthy male adults
Gait Posture
(2010) - et al.
The reliability of three-dimensional kinematic gait measurements: a systematic review
Gait Posture
(2009) - et al.
Reliability of knee biomechanics during a vertical drop jump in elite female athletes
Gait Posture
(2016) - et al.
The influence of patella alta on patellofemoral joint stress during normal and fast walking
Clin. Biomech.
(2004) - et al.
The effective quadriceps and patellar tendon moment arms relative to the tibiofemoral finite helical axis
J. Biomech.
(2015)
Sex differences in knee loading in recreational runners
J. Biomech.
Patellofemoral joint stress during stair ascent and descent in persons with and without patellofemoral pain
Gait Posture
Reliability testing of the patellofemoral joint reaction force (PFJRF) measurement during double-legged squatting in healthy subjects: a pilot study
J. Bodyw. Mov. Ther.
Patellofemoral compressive force and stress during the forward and side lunges with and without a stride
Clin. Biomech.
Differences in patellofemoral contact mechanics associated with patellofemoral pain syndrome
J. Biomech.
The effects of axial and multi-plane loading of the extensor mechanism on the patellofemoral joint
Clin. Biomech.
Inter- and intra-rater reliability of patellofemoral kinematic and contact area quantification by fast spin echo MRI and correlation with cartilage health by quantitative T1ρ MRI
Knee
Q-angle in patellofemoral pain: relationship with dynamic knee valgus, hip abductor torque, pain and function
Rev. Bras. Ortop.
Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement
Int. J. Surg.
Characteristics of foot structure and footwear associated with hallux valgus: a systematic review
Osteoarthr. Cartil.
The effects of gait retraining in runners with patellofemoral pain: a randomized trial
Clin. Biomech.
Patellofemoral joint stress during running in females with and without patellofemoral pain
Knee
Effects of step length on patellofemoral joint stress in female runners with and without patellofemoral pain
Clin. Biomech.
Sex differences in running mechanics and patellofemoral joint kinetics following an exhaustive run
J. Biomech.
Influence of a knee brace intervention on perceived pain and patellofemoral loading in recreational athletes
Clin. Biomech.
Effects of barefoot and barefoot inspired footwear on knee and ankle loading during running
Clin. Biomech.
The influence of heel height on patellofemoral joint kinetics during walking
Gait Posture
Magnetic resonance imaging of in vivo patellofemoral kinematics after total knee arthroplasty
Knee
A planar model of the knee joint to characterize the knee extensor mechanism
J. Biomech.
The orientation of the distal part of the quadriceps femoris muscle as a function of the knee flexion-extension angle
J. Biomech.
In vivo patellofemoral forces in high flexion total knee arthroplasty
J. Biomech.
Patellofemoral joint contact area increases with knee flexion and weight-bearing
J. Orthop. Res.
Patellofemoral morphology and alignment: reference values and dose-response patterns for the relation to MRI features of patellofemoral osteoarthritis
Osteoarthr. Cartilage
Lateral displacement, sulcus angle and trochlear angle are associated with early patellofemoral osteoarthritis following anterior cruciate ligament reconstruction
Knee Surg. Sports Traumatol. Arthrosc.
Basic kinematics and biomechanics of the patello-femoral joint. Part 1: the native patella
Acta Orthop. Belg.
Patellofemoral joint osteoarthritis: an important subgroup of knee osteoarthritis
Rheumatology
The associations between indices of patellofemoral geometry and knee pain and patella cartilage volume: a cross-sectional study
BMC Musculoskelet. Disord.
Patellofemoral stress during walking in persons with and without patellofemoral pain
Med. Sci. Sports Exerc.
Estimated patellofemoral compressive forces and contact pressures during dance landings
J. Appl. Biomech.
Biomechanical considerations in patellofemoral joint rehabilitation
Am. J. Sports Med.
Forces acting on the patella during maximal voluntary contraction of the quadriceps femoris muscle at different knee flexion/extension angles
Acta Anat. (Basel)
Biomechanical Basis of Human Movement
Forefoot strikers exhibit lower running-induced knee loading than rearfoot strikers
Med. Sci. Sports Exerc.
Patellofemoral joint stress during running with alterations in foot strike pattern
Med. Sci. Sports Exerc.
Patellofemoral joint force and stress during the wall squat and one-leg squat
Med. Sci. Sports Exerc.
Take your shoes off to reduce patellofemoral joint stress during running
Br. J. Sports Med.
Methodological factors affecting joint moments estimation in clinical gait analysis: a systematic review
Biomed. Eng. Online
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2023, Brazilian Journal of Physical TherapyThe effect of heel-to-toe drop of running shoes on patellofemoral joint stress during running
2022, Gait and PostureCitation Excerpt :The standing phase was the duration between the landing and subsequent toe-off. The above calculations of coefficient K, quadriceps force, moment arm, PFJ force, and stress were commended by Nunes et al. [30] based on a systematic review of commonly used methods for these calculations. The peak PFJ stress and the knee flexion angle, knee extension moment, and PFJ force at the time of peak PFJ stress were compared across heel-to-toe drop conditions using one-way ANOVAs with repeated measures.
Patellofemoral joint stress measured across three different running techniques
2019, Gait and PostureCitation Excerpt :The methodological differences, especially in the mathematical model to estimate PFJS between previous studies, have to be taken into account when interpreting and comparing the results. Recently, Nunes et al. [4] in a systematic review highlighted the relevant differences in previous investigations when considering similar methods of PFJS calculation. Despite being an indirect calculation, that considers only sagittal plane forces [4], these authors suggested that a standard method for calculating PFJS should be applied within the same experimental protocol in order to help compare effects across different gait running techniques.