Pressure Pain Thresholds In Adults With Patellofemoral Pain And Patellofemoral Joint Osteoarthritis: A Case-Control Study

Abstract

Background/Aims Patellofemoral pain and patellofemoral joint osteoarthritis are common non-self-limiting conditions. The two conditions are on a continuum with 20–30% of patellofemoral pain patients showing radiographic and magnetic resonance imaging features of patellofemoral joint osteoarthritis. Evidence suggests reduced pressure pain thresholds, locally and remotely from the site of reported pain, are a feature of patellofemoral pain in adolescent females. However, a paucity of evidence exists for male and female adults with no studies considering pressure pain thresholds in patellofemoral joint osteoarthritis. Exploring if pain sensitisation is a dominant feature of patellofemoral pain and patellofemoral joint osteoarthritis, and if a subgroup at and increased risk can be identified, may guide future treatments for instance the need for components aimed at neurological pain. The primary aim is to measure local and remote pressure pain thresholds in patellofemoral pain and patellofemoral joint osteoarthritis patients compared to matched controls. Secondary aims will consider the relationship between pressure pain thresholds and patellofemoral pain/patellofemoral joint osteoarthritis severity and knee function. Methods A total of 13 patellofemoral pain patients, 15 patellofemoral joint osteoarthritis patients and 54 age and sex matched controls were recruited from UK male and female adults. Demographic details, Tegner activity level score, symptom duration, Kujala score (for patellofemoral pain severity), Knee injury and Osteoarthritis Outcome Score score (for patellofemoral joint osteoarthritis severity) and Whatman score rating of five single leg squats (for knee function) were recorded. Pressure pain thresholds were measured at six sites: five local around the knee, one remote on the contralateral leg. Between-group differences were tested using analysis of variance techniques. Strength of association between pressure pain thresholds and patellofemoral pain/patellofemoral joint osteoarthritis severity and knee function were tested using Spearman's rank order correlation. Results No statistically significant difference in pressure pain thresholds were identified between the patellofemoral pain patients and matched controls (F(1,31)=0.687, P=0.413, h2=0.022). Similarly, no difference in pressure pain thresholds were identified between the patellofemoral joint osteoarthritis patients and matched controls (F(1,47)=0.237, P=0.629, h2=0.005). Conclusions Contrary to the hypothesis, no difference was found between patellofemoral pain nor patellofemoral joint osteoarthritis patients and matched controls.