Associations Between Pain Patterns And Pain-Related Patient-Reported Outcomes In Knee Osteoarthritis

BackgroundPain is the prominent symptom of knee osteoarthritis(OA).Pain location represents a new way to define pain patterns.Diverse locations of knee pain may reflect different tissues and structures involved in the disease process,and be related to patient-reported outcomes,including pain intensity,frequency and quality,which will ultimately influence patient' s functional and psychological status.Pain-related patient-reported outcome is a measurement of any aspect of a patient's health status related pain that comes directly from the patient.Different knee diagrams have been used to identify the location of knee pain,but some have not been validated and/or evaluated for reliability.Moreover,the classification criteria of pain location and the definition of pain pattern are variable,contributing to diverse conclusions.Further studies are needed to describe locations and patterns of knee pain,and to explore their relationships with pain-related patient-reported outcomes in knee OA.Further,no research has evaluated the relationships between pain locations or patterns and pain catastrophizing and/or pain self-efficacy in patients with knee OA,which can affect pain sensation and pain management as reported before.Objectives1.To identify pain locations and patterns in patients with knee OA.2.To determine associations between knee pain patterns and pain intensity,frequency,quality,functional limitations,and psychological status.Methods1.ParticipantsA convenience sample of 203 patients with knee OA was recruited from two Grade ? Level A hospitals in Guangzhou,from July 2016 to July 2017.2.Instruments2.1 Pain assessmentPhotographic Knee Pain Map(PKPM)was used to identify locations and patterns of knee pain.Patients indicated pain locations of the index knee upon a photograph of a pair of knees,and ticked the box below the photograph if pain was felt in the back of the knee.Then a transparent template dividing the knee into nine anterior zones in terms of anatomic marks was used to determine pain zones,which were further combined to form pain regions.Pain patterns were identified according to the location and combination of pain regions.The 0-10 Numeric Rating Scale(NRS)was used to assess knee pain intensity at rest,during activities and on average in the past week.The Intermittent and Constant Osteoarthritis Pain:KNEE Version(ICOAP:KNEE Version)was administered to evaluate constant and intermittent pain experiences in knee OA,with score range of 0-100 for the complete questionnaire and both subscales.The Pain Rating Index of the Short-form McGill Pain Questionnaire(SF-MPQ)was used to identify pain quality in this study,with score range of 0-33 for sensory subscale and 0-12 for affective subscale.2.2 Functional statusThe Knee Injury and Osteoarthritis Outcome Score(KOOS)was used to assess knee-related pain,symptoms,function in daily living,function in sport and recreation,and quality of life,with scores transformed to a 0-100 scale for analyses.2.3 Psychological statusPain Catastrophizing Scale(PCS)was used to measure catastrophizing thinking related to pain,with a score range of 0-52.Pain Self-Efficacy Questionnaire(PSEQ)was developed to assess patients' confidence in coping with pain conditions,with a score range of 0-60.3.Study proceduresParticipants completed questionnaires about pain locations and pain-related patient-reported outcomes.Demographics and clinical information were collected from the Electronic Medical Records.Then patterns of knee pain were identified.Results1.Descriptive characteristics of the study participantsPatients with knee OA suffered mild to moderate knee pain,with diverse pain qualities.The most frequent sensory descriptor was "heavy"(62.1%),and the most common affective descriptor was "sickening"(55.2%).In addition,the scores of knee-related symptoms,pain,activities of daily life,sport and recreation function and quality of life were relatively low.The medians of pain catastrophizing and pain self-efficacy were 15(IQR=9-29)and 39(IQR=29-46),respectively.2.Locations and patterns of knee painThe common knee pain zones were the medial joint line area(72.9%)and the lateral joint line area(38.4%).The common pain patterns were diffuse(34.5%),isolated medial(22.7%),isolated anterior(9.9%),and medial-lateral pain(9.9%).3.Associations between pain patterns and pain-related patient-reported outcomesDiffuse pain was associated with higher constant(P<0.001)and intermittent pain(P=0.048)scores,and more severe knee pain at rest(P=0.002),compared to isolated medial,isolated anterior and/or medial-lateral pain.Scores of knee-related symptoms(P<0.001),pain(P<0.001),activities of daily life(P=0.022),sport and recreation function(P=0.027),and quality of life(P<0.001)were worse in diffuse pain.In addition,patients with diffuse pain reported relatively high pain catastrophizing(P=0.002)and low pain self-efficacy(P=0.007)scores.Diffuse pain also was associated with worse outcomes after adjusting for confounding factors(P<0.05).ConclusionsThe most common pattern is diffuse pain in patients with knee OA,with worse knee pain intensity at rest,constant and intermittent pain experiences,physical and psychological status,compared to more localized patterns.