Is it all in the knee?
Patellofemoral pain (PFP) is considered a mechanistic pain syndrome, originating from kinetic, anatomic or biomechanical dysfunction leading to nociceptive pain. However, some data shows that not all pain expressions in patients with PFP can be causatively connected to a biomechanical impairment. Researchers from the School of Health and Rehabilitation Sciences, The University of Queensland, Australia, have endeavored to clarify whether patients suffering from PFP have local or centrally altered sensory profiles.
Profiling patients vs. controlsOne-hundred-and-fifty patients with PFP were recruited along with sixty one controls. Quantitative sensory testing (QST) was performed on the most painful knee and on a remote site: the contralateral lateral epicondyle of the elbow. QST consisted of: mechanical and thermal sensory and pain thresholds, pressure pain thresholds (PPT), as well as mechanical temporal summation and conditioned pain modulation (CPM) with PPTs as test stimuli and cold pressor as the conditioning stimulus. Medoc’s Pathway ATS, TSA2’s predecessor, was utilized for all thermal thresholds. Questionnaires on kinesiophobia (TSK), self-efficacy (FESQ), catastrophizing (PCS), and anxiety and depression (HADS) were administered.
What was foundInterestingly, cold and heat pain thresholds were significantly lower for the patient group compared to the controls, both at the knee and the elbow, hinting at central sensitization. There were similar findings for the mechanical pain and pressure pain thresholds, but not for the sensory thermal/mechanical thresholds. In pain modulation measures of temporal summation and CPM only temporal summation was significantly increased for the patient group. Additional to this, higher prevalence of anxiety, depression and pain catastrophizing was found in the patient group as compared to the controls.
To concludeThe authors conclude that “Our discovery of thermal hyperalgesia offers new insight in terms of PFP mechanisms. Multi-modal hyperalgesia locally and at a remote site (elbow), reflected by greater sensitivity to heat, cold and pressure pain in our PFP group, could be construed as evidence of nociplastic pain.” Physicians, physiotherapists and other clinicians treating patients with patellofemoral pain should take into account physiological, pain modulatory, and psychological changes, in order to holistically treat their patients.
Reference: Maclachlan, L. R., Collins, N. J., Hodges, P. W., & Vicenzino, B. (2020). Psychological and pain profiles in persons with patellofemoral pain as the primary symptom. European Journal of Pain, 24(6), 1182-1196.