Acute effects of a single bout of exercise therapy on knee acoustic emissions in patients with osteoarthritis: a double-blinded, randomized controlled crossover trial

Abstract

Background: Knee osteoarthritis is associated with higher kinetic friction in the knee joint, hence increased acoustic emissions during motion. Decreases in compressive load and improvements in movement quality might reduce this friction and, thus, sound amplitude. We investigated if an exercise treatment acutely affects knee joint sounds during different activities of daily life.

Methods: Eighteen participants with knee osteoarthritis (aged 51.8 ± 7.3 years; 14 females) were included in this randomized crossover trial. A neuromuscular exercise intervention and a placebo laser needle acupuncture treatment were performed. Before and after both interventions, knee joint sounds were measured during three different activities of daily living (standing up/sitting down, walking, descending stairs) by means of vibroarthrography. The mean amplitude (dB) and the median power frequency (MPF, Hz) were assessed at the medial tibial plateau and the patella. Differences in knee acoustic emissions between placebo and exercise interventions were calculated by analyses of covariance.

Results: Controlled for participant's age, knee demanding activity level and osteoarthritis stage, the conditions significantly differed in their impact on the MPF (mean(± SD) pre-post-differences standing up: placebo: 9.55(± 29.15) Hz/ exercise: 13.01(± 56.06) Hz, F = 4.9, p < 0.05) and the amplitude (standing up: placebo:0.75(± 1.43) dB/ exercise: 0.51(± 4.68) dB, F = 5.0, p < 0.05; sitting down: placebo: 0.07(± 1.21) dB/ exercise: -0.16(± .36) dB, F = 4.7, p < 0.05) at the tibia. There were no differences in the MPF and amplitude during walking and descending stairs (p > 0.05). At the patella, we found significant differences in the MPF during walking (placebo 0.08(± 1.42) Hz/ exercise: 15.76(± 64.25) Hz, F = 4.8, p < .05) and in the amplitude during descending stairs (placebo: 0.02 (± 2.72) dB/ exercise: -0.73(± 2.84) dB, F = 4.9, p < 0.05). There were no differences in standing up/ sitting down for both parameters, nor in descending stairs for the MPF and walking for the amplitude (p > 0.05).

Conclusion: The MPF pre-post differences of the exercise intervention were higher compared to the MPF pre-post differences of the placebo treatment. The amplitude pre-post differences were lower in the exercise intervention. In particular, the sound amplitude might be an indicator for therapy effects in persons with knee osteoarthritis.

Trial registration: The study was retrospectively registered in the German Clinical Trials Register ( DRKS00022936 , date of registry: 26/08/2020).

Keywords: Activities of daily living; Knee joint sound; Knee osteoarthritis; Neuromuscular exercise; Vibroarthrography.

Fig. 1

Microphone locations. 1 medial tibial plateau, 2 patella

Fig. 2

Pre-post differences of the pain intensity level. Comparison of placebo treatment and exercise intervention. Violin plots with median, interquartile ranges (boxes), individual values (dots) and data distribution

Fig. 3

Pre-post differences of a) the median power frequency and b) the amplitude at the medial tibial plateau between placebo treatment and exercise intervention. Violin plots with median, interquartile ranges (boxes) and data distribution with individual values (dots). A = standing up, B = sitting down, C = walking, D = descending stairs

Fig. 4

Pre-post differences of a) the median power frequency and b) the amplitude at the patella between placebo treatment and exercise intervention. Violin plots with median, interquartile ranges (boxes) and data distribution with individual values(dots). A = standing up, B = sitting down, C = walking, D = descending stairs