This clinical research study is comparing two non-surgical treatments-Low-Level Laser Therapy (LLLT) and Short Wave Diathermy (SWD)-to see which is more effective for people with a partial tear of the anterior cruciate ligament (ACL) in the knee. The ACL is a key ligament that helps keep the knee stable during movement. When partially torn, it can cause pain, weakness, and difficulty with walking or physical activities.

LLLT, also called photobiomodulation, is a painless, light-based therapy that helps reduce swelling, relieve pain, and promote healing. SWD is a type of deep heat therapy commonly used in physiotherapy to improve circulation and tissue repair.

This study will include 72 patients between 20 and 40 years old who have been diagnosed with a partial ACL tear through MRI. All participants will receive standard physiotherapy exercises and SWD, while half will also receive LLLT.

The study aims to find out if adding LLLT can:

Reduce knee pain

Improve knee muscle strength

Help patients perform daily activities more easily

Each participant will be monitored for 6 weeks, with check-ins at the start, the 3rd week, and the 6th week. Pain levels, muscle strength, and knee function will be measured using reliable assessment tools. The results of this study may help guide better treatment options for people with ACL injuries who want to avoid surgery.

Background & Rationale:

Partial anterior cruciate ligament (ACL) tears are frequent orthopedic injuries, particularly among young adults involved in sports requiring rapid pivoting or directional changes. These injuries often result in pain, instability, muscular weakness, and functional limitations. While complete ACL tears often necessitate surgical reconstruction, partial tears are typically managed with conservative approaches such as physiotherapy and adjunctive non-invasive therapies.

Low-Level Laser Therapy (LLLT), or photobiomodulation, is a non-thermal modality that promotes tissue healing through light-induced cellular stimulation. It has shown beneficial effects in reducing inflammation and pain across various musculoskeletal conditions. However, there is limited high-quality evidence evaluating its specific effects on partial ACL injuries or how it compares to widely used modalities like Short Wave Diathermy (SWD).

Study Design and Methodology:

This is a single-blinded, randomized controlled trial enrolling 72 participants aged 20-40 years with MRI-confirmed partial ACL tears. Participants are randomly assigned (n=36 each) into two groups:

Group A (LLLT + SWD + Physiotherapy): Receives Low-Level Laser Therapy in addition to standard physiotherapy and short wave diathermy

Group B (SWD + Physiotherapy): Receives standard physiotherapy and short wave diathermy only

LLLT Protocol:

Wavelength: 830 nm

Power Output: 150 mW

Power Density: 5 W/cm²

Frequency: 2-3 sessions per week for 6 weeks

Application Time: 3-4 minutes per treatment site (targeting multiple anatomical points around the knee)

Standard Physiotherapy for Both Groups:

Exercises: Heel slides, partial knee bends, quadriceps sets, step-ups

Repetitions: 2 sets of 10, with 3-5 second rest intervals

Short Wave Diathermy Protocol (Both Groups):

Frequency: 27.12 MHz

Duration: 20-30 minutes per session

Application: 2-3 sessions over baseline phase

Outcome Measures:

Assessments will be conducted at baseline, 3rd week, and 6th week using validated clinical tools:

Pain: McGill Pain Questionnaire

Muscle Strength: Handheld dynamometer (quadriceps/hamstrings)

Functional Disability: KOOS (Knee Injury and Osteoarthritis Outcome Score)

Blinding and Randomization:

Random allocation via computerized random number generation

Single-blinded: Outcome assessors blinded to group assignment

Ethical Approval and Consent:

Approved by the Ethical Review Committee at the University of Lahore

Informed written consent obtained from all participants

Privacy and confidentiality strictly maintained

Expected Impact:

This study aims to provide evidence on whether LLLT offers superior clinical outcomes in pain relief, strength enhancement, and functional recovery compared to SWD in the conservative management of partial ACL injuries. The findings may help refine treatment protocols, promote cost-effective and non-invasive rehabilitation options, and guide physiotherapists in evidence-based practice.

Inclusion Criteria:

• Pain in knee lasting more than 15 days (Masiero et al., 2020)
• Unilateral partial ACL tear diagnosed with positive lachman test and negative pivot shift test (+ve pivot shift leads to complete tear) with or without other ligament tear (Song et al., 2024)
• No other osteoarticular or soft tissue lesion (Masiero et al., 2020)

Exclusion Criteria:

• Patients with tumors or other serious diseases (Song et al., 2024)
• History of deep vein thrombosis or vascular pathology in any lower limb (Song et al., 2024)
• Rheumatoid arthritis or other signifcant co-morbidities (Masiero et al., 2020)
• Intraarticular injections into the knee in the preceding 6 months (Song et al., 2024)