The detection of knee joint sounds at defined loads by means of vibroarthrography

Crepitus of the knee may mirror structural and functional changes in the joint during motion. Although the magnitude of these sounds increases with greater cartilage damage, it is unclear whether knee joint sounds also reflect joint loading.

Twelve healthy volunteers (mean 26 (SD 3.6) years, 7 females) participated in the randomized-balanced crossover study. Knee joint sounds were recorded (linear sampling, 5512 Hz) by means of two microphones, one placed on the medial tibial plateau and one on the patella. Two activities of daily living (standing up from/sitting down on a bench; descending stairs) and three open kinetic chain knee extension-flexion cycles (passive movement, 10% and 40% loading of the individual one repetition maximum) were performed. Each participant carried out three sets of five repetitions and three sets of 15 steps downwards (stairs), respectively. For data analysis, the mean sound amplitude and the median power frequency for each loading condition were determined. Friedman test and Bonferroni-Holm adjusted post-hoc test were performed to detect differences between conditions.

We obtained significant differences between joint sound amplitudes for all movements, both measured at the medial tibial plateau (Chi² = 20.7, p < 0.001) and at the patella (Chi² = 27.6, p < 0.001). We showed a significant difference in the median power frequency of the patella between all movements (Chi² = 17.8, p < 0.5).

Overall, the larger the supposed knee joint loading was, the louder was the recorded knee crepitus. Consequently, vibroarthrographically assessed knee joint sounds can differ across knee joint loading conditions.