Physical exam and symptoms can identify inflammatory phenotype knee OA

Combining physical examination findings and patient reported symptoms can help identify knee inflammation in patients in the early stages of osteoarthritis, new research suggests.

A positive bulge sign or patellar tap in combination with patient-reported swelling or pain can improve the detection of effusion-synovitis in patients who could then be targeted for early interventions to prevent progression of inflammation, according to a study in Osteoarthritis and Cartilage.

The research, carried out by rheumatologists at the University of Arizona and the Institute of Bone and Joint Research, Kolling Institute, University of Sydney, used non-contrast MRI to evaluate the performance of  knee physical exam findings and symptoms in detecting effusion-synovitis in 344 knees with early OA and 216 knees with late OA.

Trained examiners performed bulge sign and patellar tap exams and patients reported on knee swelling and pain on straightening.

As expected, individual exam and symptoms had only a modest positive predictive value for  effusion-synovitis.

However, when used in combination, the exam and symptom reports provided improved detection rates sufficient to identify patients at increased  risk of effusion-synovitis.

In patients with early OA, prevalence of medium/large effusion-synovitis was 16% and positive findings for any of the physical exam manoeuvres and/or patient reported symptoms had a sensitivity of 81. Patients who reported no symptoms and had no positive physical exam findings had a 94.4% probability of no effusion-synovitis.

While not robust enough to rule in or rule out medium/large effusion-synovitis for clinical diagnostic purposes, the measures could be used to identify patients at high risk who might benefit from imaging screening to detect inflammation. Identifying patients at high risk could also help select participants suitable for study of the inflammatory phenotype of OA, the study authors said.

In late stage OA, exam findings and symptoms provided little information beyond prevalence, which was high at 54%, they added.

“Our findings suggest that a combination of either patient-reported swelling or pain with knee straightening and a positive bulge sign or a patellar tap could be a potentially inexpensive clinical screening method for knee inflammation,” the study authors concluded.

“Knee ultrasound could also be used as a secondary tool to confirm the presence of inflammation, as it is widely available, and less costly than MRI.

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