The Effectiveness of High-intensity Laser Therapy on Post-surgical Rehabilitation After Total Knee Arthroplasty

High-intensity laser therapy (HILT) will be delivered using the HIRO TT device (ASA S.r.l.), which employs a patented pulsed laser system (FDA-approved in 2003) based on a solid-state Nd:YAG source emitting near-infrared (NIR) radiation at a wavelength of 1064 nm. The device operates with a mean power of 10.5 W and a peak power of 3 kW.

Three treatment areas (each measuring 15 × 10 cm) will be targeted: two longitudinal areas over the quadriceps muscle and one transverse area over the knee joint.

The treatment will be delivered at a frequency of 15 Hz, with a total energy dose of 2000 J, corresponding to an energy density of 4.5 J/cm². The total treatment time will be 14 minutes and 30 seconds.

High-intensity laser therapy (HILT) will be delivered using the HIRO TT device (ASA S.r.l.), which employs a patented pulsed laser system (FDA-approved in 2003) based on a solid-state Nd:YAG source emitting near-infrared (NIR) radiation at a wavelength of 1064 nm. The device operates with a mean power of 10.5 W and a peak power of 3 kW.

Three treatment areas (each measuring 15 × 10 cm) will be targeted: two longitudinal areas over the quadriceps muscle and one transverse area over the knee joint.

The treatment will be delivered at a frequency of 15 Hz, with a total energy dose of 2000 J, corresponding to an energy density of 4.5 J/cm². The total treatment time will be 14 minutes and 30 seconds.

The sham laser intervention will be delivered using the same HIRO TT device and identical treatment procedures as the active HILT group.

The same anatomical areas (two longitudinal areas over the quadriceps muscle and one transverse area over the knee joint) will be targeted, with identical session duration and positioning.

During sham treatment, the device will remain switched on; however, no therapeutic laser emission will be delivered. This approach is intended to ensure participant blinding by replicating the visual and procedural aspects of the active intervention without providing any active therapeutic effect.

The sham laser intervention will be delivered using the same HIRO TT device and identical treatment procedures as the active HILT group.

The same anatomical areas (two longitudinal areas over the quadriceps muscle and one transverse area over the knee joint) will be targeted, with identical session duration and positioning.

During sham treatment, the device will remain switched on; however, no therapeutic laser emission will be delivered. This approach is intended to ensure participant blinding by replicating the visual and procedural aspects of the active intervention without providing any active therapeutic effect.

Knee range of motion (ROM) will be assessed bilaterally, both actively and passively, including maximum flexion and full extension.

Measurements will be obtained using a digital goniometer. The axis of rotation will be aligned with the lateral femoral condyle. The stationary arm will be aligned with the longitudinal axis of the femur, using the greater trochanter as a proximal reference point, while the movable arm will be aligned with the longitudinal axis of the fibula, using the fibular head and lateral malleolus as reference points.

ROM values will be recorded in degrees, with higher flexion values and lower extension deficits indicating better joint mobility.

Knee swelling will be assessed using circumferential measurements (cm) obtained with a flexible measuring tape.

Measurements will be performed with the participant in the supine position and the lower limbs in full extension. Circumference will be recorded at standardized anatomical landmarks: 1 cm below the inferior pole of the patella (knee joint line), 10 cm and 20 cm above the patellar base, and 5 cm below the patellar apex.

Two measurements will be taken at each site, and the mean value will be used for analysis. Higher circumference values will indicate greater swelling.

Lower limb muscle strength will be assessed using a handheld dynamometer during isometric knee extension and flexion of the operated limb.

Participants will perform three maximal voluntary isometric contractions for each movement, each lasting 5 seconds, with a 30-second rest interval between repetitions. The mean value of the three trials will be used for analysis.

For knee extension assessment, participants will be seated with the hip and knee flexed at 90°. For knee flexion assessment, participants will be positioned prone with the knee flexed at 90°. In both conditions, limb positioning will be standardized using a digital goniometer and stabilized with a fixation strap.

The dynamometer will be placed at the distal third of the leg, approximately 10 cm proximal to the ankle joint. The device will be manually stabilized by the assessor to ensure consistent positioning and minimize compensatory movements.

Higher values will indicate greater muscle strength.

The WOMAC is a patient-reported outcome measure specifically designed for individuals with knee osteoarthritis. It consists of three subscales assessing pain, stiffness, and physical function. The physical function subscale includes items related to activities of daily living such as walking, stair use, sitting, and standing.

Each item is scored on a Likert scale, and total scores are calculated by summing item responses. Higher scores indicate worse pain, stiffness, and functional limitation.