Abstract
Bone marrow edema (BME) is frequently observed on MR images in patients presenting with severe joint pain and may be present in numerous bone and joint diseases. BME may be subdivided into ischemic (bone marrow edema syndrome, BMES), mechanical and reactive BME. Although bone marrow edema of the knee is a common phenomenon, physical tests to diagnose this condition have not been investigated thus far. We hypothesized that a mallet test would be useful as a diagnostic aid as well as a screening tool.
70 patients (36 female, 34 male) were investigated in this blinded controlled study. Group 1 consisted of patients with painful BME in the knee and group 2 of patients with a painful knee without BME. Pain provoked by a reflex mallet was assessed for each quadrant on a visual analog scale (VAS).
The VAS score was 3.7 (±2.1 cm) for quadrants affected by BME (group 1), 1.59 (±1.44) in non-affected quadrants of the knee affected by BME (group 1) and, 0.85 (±0.85) in painful knees without BME (group 2). Pain on the tapping test was significantly correlated with the presence of BME in the affected knee (p< 0.0001) as well as the affected quadrant (p< 0.0001 for the medial femoral condyle and the medial femoral plateau).
The probable mode of action is that high intramedullary pressure in the BME affected bone (normal values are less than 30 mmHg) is additionally raised for a short period of time by the impact of the hammer on the bone surface, causing intense local pain. The test is economical, easy to perform in a doctor’s office, and not time-consuming but the final and evidentiary dignosis of BME can only be made by MRI.
The tapping test is a good screening instrument to diagnose BME in the knee.
Correspondence should be addressed to EORS Secretariat Mag. Gerlinde M. Jahn, c/o Vienna Medical Academy, Alserstrasse 4, 1090 Vienna, Austria. Fax: +43-1-4078274. Email: eors@medacad.org
