title: Efficacy of interferential low-level laser therapy using two independent sources in the treatment of knee pain.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effectiveness of an interferential pattern generated by two identical and independent lasers in the relief of knee pain.
  
  
  BACKGROUND
  Low-level laser therapy (LLLT) is generally applied by a single probe.
  
  
  METHODS
  A double-blind controlled clinical trial was performed on 152 patients with knee pain who were randomly assigned into two different groups. Group I patients (n = 76) received interferential laser therapy generated by two identical laser probes located opposite each other on the knee joint. Group II patients (n = 76) received one live probe in conventional laser therapy and one dummy probe. The device used in both groups was an AlGaAs laser (wavelength 810 nm, power 100 mW, in continuous mode). Fifteen laser sessions were applied transcutaneously on 5 knee points (6 J/point) per session. In addition, patients in both groups received a quadriceps strength program based on isometric exercises. A visual analogue scale (VAS) was used for pain evaluation in different situations, such as in standing, in knee flexion/extension, and when going up and down stairs. VAS pain scores were evaluated before, in the middle of, and after treatment.
  
  
  RESULTS
  ANOVA results showed no significant differences between groups for all VAS scores or in the interaction with the sessions (p > 0.05). The VAS score results showed a statistically significant pain reduction throughout all sessions (p = 0.000).
  
  
  CONCLUSIONS
  Interferential laser therapy is safe and effective in reducing knee pain. However, the results of the study indicate that it is not superior to the use of a single conventional laser.
authors.affiliation: Unit of Physiotherapy, Hospital Ramón y Cajal, Madrid, Spain. rasolabea@telefonica.net
authors.forename: Ramón
authors.initials: R
authors.lastname: Montes-Molina
authors.forename: Maria Antonia
authors.initials: MA
authors.lastname: Madroñero-Agreda
authors.forename: Ana Belen
authors.initials: AB
authors.lastname: Romojaro-Rodríguez
authors.forename: Vanessa
authors.initials: V
authors.lastname: Gallego-Mendez
authors.forename: Carolina
authors.initials: C
authors.lastname: Prados-Cabiedas
authors.forename: Cesar
authors.initials: C
authors.lastname: Marques-Lucas
authors.forename: Monica
authors.initials: M
authors.lastname: Pérez-Ferreiro
authors.forename: Fidel
authors.initials: F
authors.lastname: Martinez-Ruiz
mesh_terms: D000704:Analysis of Variance; D004311:Double-Blind Method; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D007717:Knee; D028022:Low-Level Light Therapy; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000532:radiotherapy*; D010147:Pain Measurement; D016896:Treatment Outcome