Pain and psychological characteristics in patellar tendinopathy

Abstract

Introduction: Patellar tendinopathy (PT) is a common injury in sports and is characterized by persistent pain and interference with physical activity. Evidence from other persistent musculoskeletal pain states has shown alterations in somatosensory profiles implicating central nervous system involvement. The aim was therefore to assess detection and pain thresholds in patients with persistent PT compared with healthy controls. Methods: The following Quantitative Sensory Testing (QST) was performed in 19 people with PT (age 20–45 years; 26% female) and 15 healthy controls (age 21–33 years; 53% female): warmth and cold detection, thermal sensory limen, heat and cold pain, mechanical detection threshold, mechanical pain threshold, mechanical pain sensitivity, dynamic mechanical allodynia, vibration disappearance threshold, wind up ratio and pressure pain threshold (PPT). The assessor was blinded to the participant group. Testing in patients and controls was performed at two standardized locations; over the infra patellar pole (most affected or randomly allocated leg respectively) and the lateral elbow (randomly allocated arm). The VISA-P, Health-related Quality of Life (EQ-5D), the Hospital Anxiety and Depression Scale (HADS), the Active Australia Questionnaire and the Mental Toughness Questionnaire (MTQ-48) were completed by all participants. ANCOVA was performed to compare groups, adjusting for sex, age and BMI. Ordinal data was assessed with non-parametric Mann Whitney U tests. Results: PPT measured at the proximal patellar tendon was significantly lower in the PT group (408.8 kPa) compared to controls (568.5 kPa) after adjusting for sex, age and BMI (P = 0.012). No between-group differences were found for any other QST measures at either the inferior pole or lateral elbow. The PT group had significantly lower quality of life scores (P < 0.001) and significantly higher mental toughness scores (P < 0.05) compared to controls. No differences existed between groups for anxiety, depression and physical activity. Discussion: Significantly lower PPT scores for people with PT compared to healthy controls suggests peripheral mechanical hyperalgesia. The lack of evidence of central sensitization may be different to other tendinopathies. Although people with PT have a lower quality of life, they also seem to be more mentally tough than healthy controls. Further research should elaborate on this personality trait as well as the negative and positive influences it might have on the development and rehabilitation of injuries.