Tapping test in patients with painful bone marrow edema of the knee.
BACKGROUND
Although bone marrow edema (BME) of the knee is a common phenomenon, physical tests to diagnose this condition have not been investigated. We hypothesized that a mallet test would be useful as a diagnostic aid and a screening tool.


METHODS
Seventy patients (36 female, 34 male) were investigated in this 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).


RESULTS
The VAS score was 3.7 (+/-2.1 cm) for quadrants affected by BME (group 1), 1.59 (+/-1.44) in nonaffected 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) and the affected quadrant (P<0.0001 for the medial femoral condyle and the medial femoral plateau). A threshold value of VAS 2.0 for a tapping test to be positive in the distinction of BME affected quadrants of group 1 and all quadrants of group 2 sensitivity was 90.4%, specificity 83.7%, positive predictive value 73.4%, and negative predictive value 94.6% was determined.


CONCLUSIONS
The tapping test is a good screening instrument to diagnose BME in the knee.
Aigner
Nicolas
N
The Orthopaedic Hospital Vienna-Speising, Speisingerstr, Vienna, Austria. nicolas.aigner@oss.at
Meizer
Roland
R
Meraner
Dominik
D
Becker
Stephan
S
Radda
Christian
C
Landsiedl
Franz
F
D000328:Adult; D018771:Arthralgia / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D001853:Bone Marrow / Q000503:physiopathology; D018450:Disease Progression; D004487:Edema / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination / Q000295:instrumentation / Q000379:methods; D010020:Osteonecrosis / Q000503:physiopathology / Q000517:prevention & control; D010147:Pain Measurement / Q000295:instrumentation / Q000379:methods*; D017288:Pain Threshold / Q000502:physiology; D010812:Physical Stimulation / Q000295:instrumentation / Q000379:methods; D011237:Predictive Value of Tests; D012021:Reflex, Abnormal / Q000502:physiology