Original researchFeasibility and reliability of pain pressure threshold measurements in patellar tendinopathy
Highlights
► We investigated the use of pain pressure threshold algometry in patellar tendinopathy. ► Athletes with and without patellar tendinopathy were measured. ► We analyzed feasibility, inter-rater and intra-rater reliability. ► Pain pressure threshold algometry is a feasible and reliable method to standardize pain measurements in patellar tendinopathy.
Introduction
Patellar tendinopathy (PT) refers to a clinical condition characterized by activity-related anterior knee pain associated with focal patellar tendon tenderness.1 The overall prevalence of PT in elite athletes is estimated at 14.2% with the highest prevalence in volleyball (44.6%) and basketball (31.9%).2 Athletes with PT sometimes have to reduce their training and competition levels or even have to end their sport career.3
The etiology and pain mechanisms of PT are not completely understood. Patellar tendinopathy is considered to be an ‘overuse injury’ with a failed healing response to repetitive microtrauma.4, 5 The diagnosis is based primarily on clinical examination and history taking. Activity related anterior knee pain and focal patellar tendon pain on palpation are almost pathognomonic for this condition. Ultrasonography (US) and magnetic resonance imaging (MRI) can be used to increase the likelihood of the diagnosis although the sensitivity and specificity of these methods are poor.6 Besides a clinical examination the Victorian Institute of Sports Assessment – Patellar (VISA-P) questionnaire is frequently used to evaluate symptoms of PT and their effects on physical activity.7
Manual palpation plays an important role not only in diagnosing PT but also in the evaluation of rehabilitation programs. During this palpation the examiner applies manual pressure on the patellar tendon and patients are asked whether this is painful. The reliability of palpation depends on the application technique of the examiner.8 Manual palpation is difficult to standardize and shows moderate sensitivity and specificity.6, 9
Palpation pressure and the evoked pain can be measured in a standardized way by using an algometer. This device enables the application of a known force – calibrated in Newtons – to the skin and underlying tissue. By gradually increasing the force of the algometer, the “pressure pain threshold” (PPT) can be determined. This method is widely used and several studies have demonstrated that algometry yields reliable and reproducible results in a number of patient groups.10, 11, 12
In the clinical assessment and treatment evaluation of athletes with PT the algometer might be useful to measure pain thresholds in an objective way. So far, the use and reliability of instrumental algometry in athletes with PT have not been reported in the literature. The purposes of this study were: First to investigate the feasibility of conducting PPT measurements in athletes with a diagnosed PT. Second to determine if PPT in asymptomatic athletes differs from athletes with a PT. Third to analyze the inter- and intra-rater reliability and the clinically relevant limits of agreement of PPT in athletes with PT.
Section snippets
Methods
To measure ‘normal’ PPT in asymptomatic athletes, 10 female and 10 male asymptomatic volunteer volleyball players were included. Inclusion criteria were: aged between 18 and 35 without knee pain in the last year and with a VISA-P score of 95–100. The inter-rater reliability component of the study included 54 athletes with symptomatic PT, while the intra-rater reliability study included another group of 48 athletes with PT. The following inclusion criteria were applied for athletes with a PT:
Results
During testing observers reported difficulties measuring athletes with the most painful spot at the origin of the patellar tendon, just underneath the patella, sometimes with finding the most painful spot and difficulties with skin shift after marking the most painful spot.
The asymptomatic volleyball players had a mean age of 21.0 (SD 3.1). They were measured twice on the left patella tendon (one missing) and on the right tendon. Of the 78 measurements, 67 (86%) reached the maximum pressure of
Discussion
Standardized PPT algometry seems to be a feasible test method in athletes with PT. The pain pressure thresholds of asymptomatic volleyball players differ significantly from athletes with a diagnosis of PT. The inter-rater reliability is adequate and the intra-rater reliability moderate. A change of more than 19 N can be used to identify a significant change of PPT in athletes with a PT.
The ICC showed adequate reliability for the inter-rater reliability, these high ICC have also been reported in
Conclusion
Although further research is warranted PPT algometry seems to be a feasible, reliable and useful tool in the diagnosis and treatment evaluation of athletes with patellar tendinopathy.
Practical implications
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PPT-algometry seems a feasible method for the use in the diagnosis and follow-up of athletes with patellar tendinopathy.
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The PPTs of athletes with PT differ significantly from asymptomatic athletes.
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The inter-rater (ICC 0.93) and intra-rater (ICC 0.60) reliability of the PPT in patella tendinopathy are adequate to moderate.
Acknowledgements
The authors would like to thank all the participating athletes, Jorrian Hop (student, Human Movement Sciences, University Medical Center Groningen, University of Groningen) and Anneke Beetsma (lecturer, Hanze University Groningen, University of Applied Sciences).
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