Effect of Low-Intensity Pulsed Ultrasound on the Cartilage Repair in People With Mild to Moderate Knee Osteoarthritis: A Double-Blinded, Randomized, Placebo-Controlled Pilot Study

OBJECTIVE: To determine the feasibility of conducting a randomized controlled trial assessing the effect of low-intensity pulsed ultrasound (US) therapy on cartilage repair in patients with mild to moderate knee osteoarthritis (OA). DESIGN: Pilot, double-blinded, randomized placebo-controlled trial with 2-months follow-up. SETTING: Rehabilitation research facility. PARTICIPANTS: Adults (N=27; ≥45y) with grades 1 or 2 of medial joint space narrowing (Osteoarthritis Research Society International atlas) due to knee OA were randomly allocated to receive active (n=14) or sham (n=13) US therapy. Four participants withdrew for personal reasons. INTERVENTIONS: Twenty-four sessions of active (20% duty cycle, 1MHz, average temporal intensity: 0.2W/cm(2), therapeutic dose: 112.5J/cm(2)) or sham (no sound-head crystal) US therapy. MAIN OUTCOME MEASURES: Success of recruitment and adherence rates were established by a priori criteria. Effect on cartilage repair was assessed by measuring cartilage volume and thickness and scoring cartilage injury, subchondral cyst formation, and bone marrow lesions on magnetic resonance images. RESULTS: Patient recruitment and adherence rates were successful. No significant age-adjusted differences were seen between groups in the cartilage repair outcomes. Age-adjusted analyses, including only subjects who attended 20 sessions or more, showed an increase in medial tibia cartilage thickness in the active US therapy group (90μm; 95% confidence interval, 1-200; P=.05). CONCLUSIONS: Conducting a randomized controlled trial to assess the effects of US therapy on the cartilage repair in people with mild to moderate knee OA is feasible. However, further pilot studies are needed to determine the optimal US dose and application parameters before designing a full trial.