Estimating the probability of radiographic osteoarthritis in the older patient with knee pain.

OBJECTIVE: To determine whether clinical information can practically rule in or rule out the presence of radiographic osteoarthritis in older adults with knee pain.
METHODS: We conducted a cross-sectional diagnostic study involving 695 adults ages >/=50 years reporting knee pain within the last year identified by postal survey and attending a research clinic. Potential indicators of radiographic osteoarthritis were gathered by self-complete questionnaires, clinical interview, and physical examination. Participants underwent plain radiography (posteroanterior, skyline, and lateral views). Radiographic osteoarthritis was defined as the presence of definite osteophytes in at least 1 joint compartment of the index knee.
RESULTS: Independent predictors of radiographic osteoarthritis were age, sex, body mass index, absence of whole leg pain, traumatic onset, difficulty descending stairs, palpable effusion, fixed-flexion deformity, restricted-flexion range of motion, and crepitus. Using this model, 245 participants had a predicted probability >/=80% (practical rule in), of whom 231 (94%) actually had radiographic osteoarthritis (specificity 93%). Twenty-one participants had a predicted probability <20% (practical rule out), of whom only 2 (10%) had radiographic osteoarthritis (sensitivity 99.6%). The predicted probability of radiographic osteoarthritis for the remaining 429 participants fell into an intermediate category (20-79%).
CONCLUSION: Simple clinical information can be used to estimate the probability of radiographic osteoarthritis in individual patients. However, for the majority of community-dwelling older adults with knee pain this method enables the presence of radiographic osteoarthritis to be neither confidently ruled in nor ruled out. Prospective validation and updating of these findings in an independent sample is required.