MOST has conducted five follow-up contacts with patients at 15, 30, 60, 72 and 84 months, with a current visit ongoing for the 144-month follow-up. Clinical assessments are conducted at each visit, with radiological data, both X-rays and MRI, collected, as well as other measures and instruments. The 72-month follow-up, however, included only a telephone interview. There are three investigative aims: mechanical risk factors, causes of knee symptoms and pain, and long-term disease trajectory of knee OA, according to an overview of the study.3
Overall goals of the study are to understand the risk factors, natural history and consequences of OA. MOST investigators hope to identify novel and modifiable biomechanical factors, including physical activity-related factors, bone and joint structural factors, and nutritional factors that affect the occurrence and progression of OA-related knee symptoms and radiographic knee OA. Investigators involved in the study are seeking to determine whether risk factors for onset of disease are different than those responsible for the progression of the disease.
Dr. Neogi and colleagues involved in the pain sensitization research collected data from MOST in subjects who had attended the 60-month and 84-month study visits, which were the first visits where standardized quantitative sensory testing measures of sensitization were obtained. The data on subjects included standardized and validated assessments, including radiographs, MRIs and bone density scans; answers to questionnaires related to various aspects of pain, function, sleep, depressive symptoms, other psychological factors and quality of life; and information about other medical conditions and medications, among others, Dr. Neogi says. Information was also available on several objective assessment measures of the patients’ strength, gait speed, chair stands, physical activity, etc., and the research team also obtained biospecimens from the patients.
Longitudinal Changes
This was the first study to examine the relation of inflammatory lesions and bone marrow lesions to concurrent and longitudinal changes in pain sensitization in a large, well-characterized cohort. Among the findings was that patients with synovitis at baseline (the 60-month visit was considered the baseline visit in this research) had a significantly lower pressure pain threshold at baseline and a significant decrease in pressure pain threshold at the patella 24 months later (the 84-month follow-up visit), which indicated that they had become more sensitized.
Effusion was associated with development of new temporal summation (which is an increase in pain when the same stimulus is repeated over time) at the patella and with a decrease in pressure pain threshold at the wrist, and “both findings suggest the involvement of central sensitization. Thus, inflammation appears to influence the development of and perhaps amplification of sensitization,” according to the researchers.