About MOST

Multicenter Osteoarthritis Study Overview and Objectives

Osteoarthritis (OA) is the most common form of arthritis and the major cause of activity limitation and physical disability in older people. More than half of those over the age of 65 have radiological evidence of osteoarthritis in at least one joint. By 2030, approximately 20 percent of Americans (about 70 million people) will have passed their 65th birthday and will be at increased risk for the disease. Today, 39 million people (13 percent of the U.S. population) are 65 and older, and more than half have developed OA.

The Multicenter Osteoarthritis Study (MOST) is a longitudinal, prospective, observational study of knee OA in older Americans with OA disease or at increased risk of developing it. The study is comprised of two clinical centers, a data coordinating center, and an analysis center.

MOST enrolled 3,026 study participants and has conducted five follow-up contacts at 15, 30, 60, 72, and 84 months. At each time point, clinical assessments were conducted and radiological data (x-ray and MRI) collected, as well as other measures and instruments, with the exception of the 72-month follow-up, which was a Telephone Interview only.

The overall aims of MOST are to identify novel and modifiable biomechanical factors (including physical activity-related factors), bone and joint structural factors (including those assessed by MRI of the knee), and nutritional factors that affect the occurrence and progression of OA-related knee symptoms and radiographic knee OA. Additionally, MOST investigators aim to determine whether risk factors for new disease differ from those for OA progression. The MOST cohort has been followed through 84 months with three investigative themes: mechanical risk factors, causes of knee symptoms and pain, and the long term disease trajectory of knee OA.

To achieve these aims, we recruited a community-based sample of 3,026 (101% of our goal) men and women aged 50 to 79 and drawn from the general population but selected so as to be likely to either have preexisting OA or be at high risk as indicated by weight, knee symptoms, or a history of knee injuries or operations. Approximately 15% of the cohort are African Americans and 60% are women. Baseline exams began in 2003 and included an assessment of risk factors and disease characteristics, knee radiographs and knee MRIs, and a musculoskeletal examination to identify knee symptoms that do not emanate from the knee or hip joint. Knee MRIs were acquired with a 1.0 T dedicated extremity MR scanner (GE Healthcare).

MOST participant retention is excellent, as summarized in the tables below.


Retention Success in MOST: Follow-up Data Collected by Time Point, Gender, and Racial Background


  Total (All)
  Enrolled1 Data collected2
Baseline 3026 3026 (100%)
15 months 3018 3007 (100%)
30 months 2993 2969 (99%)
60 months 2882 2768 (96%)
72 months 2778 2715 (98%)
84 months 2721 2638 (97%)

1 "Enrolled" means enrolled at baseline and continuing participation (not deceased and not withdrawn).
2 "Data collected" means all or some data collected (measurements and exams completed or partially completed).


  White Non-white
  Enrolled  Data collected Enrolled  Data collected
Baseline 1501 1501 (100%) 319 319 (100%)
15 months 1500 1495 (100%) 319 317 (99%)
30 months 1492 1485 (100%) 316 313 (99%)
60 months 1445 1410 (98%) 302 280 (93%)
72 months 1401 1379 (98%) 293 277 (95%)
84 months 1380 1346 (98%) 287 270 (94%)


  White Non-white
  Enrolled  Data collected Enrolled  Data collected
Baseline 1018 1018 (100%) 188 188 (100%)
15 months 1012 1011 (100%) 187 184 (98%)
30 months 1002 997 (100%) 183 174 (95%)
60 months 960 928 (97%) 175 150 (86%)
72 months 915 906 (99%) 169 153 (91%)
84 months 890 872 (98%) 164 150 (91%)

Biological specimen samples (blood and urine) were collected at baseline, 30 months, and 60 months. 

Longitudinal readings of baseline, 15-month, 30-month, 60-month, and 84-month knee x-rays have been completed. Semiquantitative readings of selected baseline, 15-month, 30-month, 60-month, and 84-month knee MRIs have been completed.

MOST is funded through grants from the National Institutes of Health / National Institute on Aging (NIA): U01 AG18820 (David Felson, Boston University); U01 AG18947 (Cora E. Lewis, University of Alabama at Birmingham); U01 AG18832 (James Torner, University of Iowa); U01 AG19069 (Michael Nevitt, University of California, San Francisco). This rich database will provide valuable information to help identify and define modifiable biomechanical, bone and structural, nutritional, and other risk factors for new disease and progression of existing disease.