Short-term effectiveness of high- and low-intensity percutaneous electrolysis in patients with patellofemoral pain syndrome: A pilot study

BACKGROUND: Unilateral patellofemoral pain syndrome (PFPS) is the most frequently diagnosed knee condition in populations aged < 50 years old. Although the treatment of myofascial trigger points (MTrPs) is a common and effective tool for reducing pain, previous studies showed no additional benefits compared with placebo in populations with PFPS. Percutaneous electrolysis is a minimally invasive approach frequently used in musculotendinous pathologies which consists of the application of a galvanic current through dry needling (DN). AIM: To evaluate changes in sensitivity, knee pain perception and perceived pain during the application of these three invasive techniques. METHODS: A triple-blinded, pilot randomized controlled trial was conducted on fifteen patients with unilateral PFPS who were randomized to the high-intensity percutaneous electrolysis (HIPE) experimental group, low-intensity percutaneous electrolysis (LIPE) experimental group or DN active control group. All interventions were conducted in the most active MTrP, in the rectus femoris muscle. The HIPE group received a 660 mA galvanic current for 10 s, the LIPE group 220 mA × 30 s and the DN group received no galvanic current. The MTrP and patellar tendon pain pressure thresholds (PPTs) and subjective anterior knee pain perception (SAKPP) were assessed before, after and 7 d after the single intervention. In addition, perceived pain during the intervention was also assessed. RESULTS: Both groups were comparable at baseline as no significant differences were found for age, height, weight, body mass index, PPTs or SAKPP. No adverse events were reported during or after the interventions. A significant decrease in SAKPP (both HIPE and LIPE, P < 0.01) and increased patellar tendon PPT (all, P < 0.001) were found, with no differences between the groups (VAS: F = 0.30; η(2 )= 0.05; P > 0.05; tendon PPT immediate effects: F = 0.15; η(2 )= 0.02; P > 0.05 and tendon PPT 7-d effects: F = 0.67; η(2 )= 0.10; P > 0.05). A significant PPT increase in rectus femoris MTrP was found at follow-up in both the HIPE and LIPE groups (both, P < 0.001) with no differences between the groups (immediate effects: F= 1.55; η(2 )= 0.20; P > 0.05 and 7-d effects: F = 0.71; η(2 )= 0.10; P > 0.05). Both HIPE and LIPE interventions were considered less painful compared with DN (F = 8.52; η(2 )= 0.587; P < 0.01). CONCLUSION: HIPE and LIPE induce PPT changes in MTrPs and patellar tendon and improvements in SAKPP, and seem to produce less pain during the intervention compared with DN.