Participants in the experimental PNM group will receive ultrasound-guided percutaneous neuromodulation of the saphenous nerve in the painful leg.

In this study, a neurostimulation device ITO ES-160 will be used, where parameters of 2 Hz, 250 μs, and 16 minutes of continuous current will be set, with an appropriate intensity for subjects to perceive nerve stimulation along the path of the nerve (from the needle insertion point to the anterior aspect and below the knee), always ensuring it remains tolerable for them. No motor response will be observed. The black clip of channel 1 will be attached to the needle, and a TENS patch will be attached to the red clip.

The interventions will be conducted 3 times, with 1 week between the first two and a 2-week interval between the second intervention and the third. All measurements will be taken before and after the procedure.

Participants in the control NON-PNM group will receive saphenous nerve puncture in the injured leg with subsequent placement of the clamps but without activating the electrostimulation function.

The needle will remain without current for 16 minutes. The interventions will be conducted 3 times, with 1 week between the first two and a 2-week interval between the second intervention and the third. All measurements will be taken before and after the procedure.

Percutaneous ultrasound-guided neuromodulation of the saphenous nerve in subjects with patellofemoral pain to assess its positive effects on pain and functionality.

To quantify "pain intensity," the Visual Analog Scale (VAS) will be used, allowing the patient to subjectively express the intensity of their pain. It consists of a 10 cm line, where one end represents complete absence of pain and the other end represents the maximum possible intensity of pain. The patient is asked to mark on the line the point that reflects their pain level, and the measurement is recorded in millimeters. Within the "pain intensity" variable, a sub-variable will record the difference in pain intensity before and after the invasive physiotherapy intervention, expressed as a percentage of relief. This approach will allow observation of pain evolution across different sessions and evaluation of the immediate effects of Percutaneous Ultrasound-guided Neuromodulation.

The Kujala Knee Pain Score (AKPS) will be primarily measured, consisting of 13 items related to specific symptoms and aggravating activities associated with patellofemoral pain (e.g., stairs, squatting, prolonged sitting, pain). Participants select a response for each item. All items are scored on a weighted basis and summed to give a score out of 100, where 0 represents maximum disability and 100 represents no disability.

The subject to be evaluated will be positioned at the edge of the examination table with 85º of hip flexion and 90º of knee flexion. A padded strap will be placed 5 cm proximal to the lateral malleolus, attached to the pressure dynamometer, which in turn will be connected to a rigid strap. This setup allows for the assessment of isometric quadriceps contraction strength. Participants will perform a warm-up consisting of five submaximal and maximal isometric knee extension contractions (50-100% effort). Subsequently, they will perform 3 maximal isometric contractions lasting 3 seconds each, with 1 minute of rest between contractions. Finally, the highest force contraction will be recorded for data analysis.