Effects of Trigger Point Dry Needling on Neuromuscular Performance and Pain of Individuals Affected by Patellofemoral Pain: A Randomized Controlled Trial

Patellofemoral pain syndrome (PFPS) is one of the most common causes of knee pain in young adults, accounting for 25-30% of cases seen in sports medicine clinics. This condition, characterized by diffuse pain behind and around the patella, is aggravated by activities such as squatting, prolonged sitting, and climbing stairs, significantly impacting the ability to exercise and perform daily activities. This randomized controlled trial investigated the efficacy of trigger point dry needling (TrP-DN) as a treatment for this debilitating condition. The research involved 50 patients diagnosed with PFPS, ages 18 to 40 years, who were randomized into two groups of 25 participants each.

The experimental group received dry needling targeting active trigger points in the vastus medialis obliquus, vastus lateralis, and rectus femoris muscles, while the control group received sham (placebo) needling. Both groups performed daily static stretching exercises of the quadriceps. The treatment protocol consisted of one session per week for 6 weeks, followed by 3 months of follow-up. Trigger points were identified using specific criteria including the presence of a palpable taut band, pain reproduction with compression, local twitch response, and referred pain.

The needling technique followed the "fast-in/fast-out" method described by Hong, using disposable stainless-steel needles. The results demonstrated significant superiority of real dry needling compared with placebo. In the treated group, the visual analog scale (VAS) for pain decreased from 46.67 points at baseline to 10.48 points after 6 weeks of treatment, remaining at 6.19 points after 3 months. In contrast, the placebo group showed a smaller and unsustained reduction.

Function, assessed by the Kujala scale, showed remarkable improvement in the experimental group, increasing from 66.42 to 90.68 points at 6 weeks and remaining at 92.21 points at the 3-month follow-up. Particularly interesting was the assessment of neuromuscular coordination through the VMO/VL (vastus medialis obliquus/vastus lateralis) ratio, measured by surface electromyography during isokinetic contractions. This ratio is considered an important indicator of muscle balance in the quadriceps and is frequently altered in PFPS. The treated group showed significant improvement in this ratio, increasing from 0.79 to 0.91, while the placebo group showed no significant changes.

The clinical implications of this study are substantial. Dry needling offers a specific and effective therapeutic approach to treating myofascial trigger points that contribute to pain and dysfunction in PFPS. The technique demonstrated not only symptomatic relief, but also improvement in neuromuscular function, suggesting benefits that go beyond simple pain control. The maintenance of benefits for 3 months indicates the potential for lasting effects.

The proposed mechanism involves interrupting the vicious cycle of muscle contracture, local ischemia, and nociceptive sensitization characteristic of trigger points. Precise needling of these points may restore local microcirculation, reduce excessive acetylcholine release, and normalize neuromuscular junction function. However, the study presents some important limitations. The sample size of 50 participants, although statistically adequate, is relatively small for broad generalization of results.

The lack of a record of the exact number of trigger points treated in each participant may have introduced variability into the results. Additionally, supervision of home-based stretching exercises was limited, which could influence outcomes. The neuromuscular coordination assessment was restricted to a single angular velocity (60°/s), not exploring other velocities or isometric contractions.