Pain Phenotypes in Knee Osteoarthritis
Condition: Osteoarthritis, Knee; Pain
MeSH terms: Osteoarthritis; Osteoarthritis, Knee
Study type: Observational

Summary: 
      Recently, the medical community has learned damage to the knee joint may be one of many
      possible reasons for pain in knee osteoarthritis. Psychological factors and other aspects of
      brain function seem to play an important role in the pain experience. Although research
      studies have examined these factors on an individual basis, no study has examined all of
      these factors in the same population. Furthermore, some measures of brain function- having to
      do with perception of the painful body part- have yet to be examined in knee osteoarthritis.
      The investigators plan to study many of these variables in a group of people with knee
      osteoarthritis, as well in some healthy controls (without knee pain), in order to establish
      the relative importance of these measures in contributing to pain, as well as validate new
      measures of perception in people with knee osteoarthritis. We also plan to use a statistical
      tool- known as latent profile analysis- to look at subgroups of knee osteoarthritis pain. The
      hypothesis is that different people experience pain in knee osteoarthritis for different
      reasons. This study will be the first study to use all of these different variables- which
      can be reproduced in a clinical setting- to look for different subgroups of knee
      osteoarthritis pain. Ultimately, the goal is to help clinicians better prioritize and target
      interventions to individual patients. The investigators believe this will lead to better
      outcomes and fewer treatment complications currently associates with pharmaceutical and
      surgical interventions that are widely used to treat knee osteoarthritis.
    

Detailed description: 
      In a 2011 statement to the Food and Drug Administration, the Osteoarthritis Research Society
      International (OARSI) identified the "phenotyping" of OA pain as a research priority to
      "better target pain therapies to individual patients." Successful identification of pain
      phenotypes will allow new interventions to be tested in homogeneous populations of patients
      presenting with similar pain pathophysiology, ultimately enhancing treatment effects in
      defined populations for whom interventions are determined safe and effective. Clinical
      populations of knee OA are clearly heterogeneous, spanning wide age ranges and encompassing
      patients with a wide variety of functional abilities. The pain experience in knee OA may be
      similarly individualized and complex; some patients may present with pain that appears
      attributable to classic signs of joint damage, while others may present with pain due to
      psychological distress or central mechanisms. Changes in somatosensory processing and pain
      threshold are also known to occur with aging. However, the scientific community has yet to
      examine these variables concurrently in the same study population. Therefore, the relative
      importance of each of these measures in determining pain severity across the lifespan is
      unknown. It is also unknown whether these variables (or interactions between variables) are
      representative of different pain phenotypes in knee OA. This is an important yet unresolved
      question; a patient with high levels of psychological distress and low levels of joint damage
      may warrant a different intervention strategy than the traditional knee-directed approach. On
      the other hand, someone with increased psychological distress in addition to severe joint
      damage may benefit from traditional interventions that are further augmented with other
      impairment-specific interventions. This sort of targeted approach is the topic of current
      research in other chronic pain populations, where a similar conceptual model, composed of
      peripheral, psychological and central components to the pain experience (among others), is
      recognized.
    

Intervention name(s): Knee Osteoarthritis; Healthy Control
Intervention type(s): Other; Other
Intervention description(s): Questionnaire completion, strength testing, gait testing, pressure-pain threshold testing, proprioception testing, knee measurements, blood draw, and knee radiographs.; Questionnaire completion, strength testing, gait testing, pressure-pain threshold testing, proprioception testing, and knee measurements.
Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Study subject population will include 50-85 year olds who experience knee pain and have
        been diagnosed with knee osteoarthritis by a physician. Additionally, a healthy control
        cohort will be recruited. This cohort will also be 50-85 years old but will deny having any
        pain and will not be diagnosed with knee osteoarthritis.
      
Biospecimen description: 
      1mL of whole blood will be taken for analysis of inflammatory factors including IL-1beta,
      IL-6, IL-8, TNF, and C-Reactive Protein. Samples will be stored at University of Colorado
      Hospital until analysis is complete. Samples will then be destroyed.
    
Keywords: Knee pain; Knee Osteoarthritis