Literature Reviews
Young Females with Long-Standing Patellofemoral Pain Display Impaired Conditional Pain Modulation, Increased Temporal Summation of Pain, and Widespread Hyperalgesia
Holden S, Straszek CL, Rathleff MS, et al. Pain 2018; 159(12):2530-7
Patellofemoral pain (PFP) is a common knee pain condition, particularly in adolescent girls. It is associated with pain-related decreased physical activity and quality of life. PFP is often recurrent and persistent over years despite treatment. Patients with PFP are known to have lower pressure pain thresholds around the knee and elbow, suggesting widespread hyperalgesia, spreading of sensitization locally and facilitation of central pain mechanisms. The tests temporal summation of pain (TSP) and conditioning pain modulation (CPM) can evaluate pro-nociceptive and anti-nociceptive central mechanisms, respectively. This study aimed to compare TSP, CPM, localized and widespread pain sensitivity in three groups of females: 1. current longstanding PFP, 2. history of PFP – now self-reported recovered, and 3. pain-free control.
Methods
The study was an assessor-blinded, matched cross-sectional study of the three groups from a population-based adolescent school population in Denmark. Following assessments five years prior, 151 patients diagnosed with PFP and 250 without musculoskeletal pain were re-contacted for inclusion in a prospective cohort. Based on a questionnaire and random selection patients were invited to participate with the primary aim of CPM guiding sample size selection. Assessment included self-reported pain and function-related measures, QST, CPM, TSP, and pressure pain thresholds by cuff algometry.
Results
A total of 87 females were recruited with 36 in the current and 22 in the recovered PFP, plus 29 controls. Participants with current PFP also often had pain in other locations (60%). Seven fulfilled criteria for widespread pain. Females with current PFP had impaired CPM effect (less descending pain inhibition) compared to the recovered group, plus facilitated TSP, and local and widespread pressure hyperalgesia compared to control. The recovered group had a greater CPM effect than group 1. There was no difference for TSP between group 1 and 2, both were increased relative to group 3. Both groups with PFP demonstrated greater pressure sensitivity compared to controls.
Conclusion
This study demonstrated altered pain mechanisms in females with a history of PFP but who are currently pain free. Increased pain sensitivity and facilitated pro-nociceptive mechanisms may predispose them to subsequent pain episodes even with limited nociceptive input. Further research is needed to assess any relationship between pain of PFP and the development and profile of altered pain mechanisms over time. (Comment: smaller sample size in two groups than desired in study design)
