1 Introduction

Shoulder pain and dysfunction are among the most common musculoskeletal health problems, affecting 16%–21% of adults and growing more common as people get older. Rotator cuff (RC) tears are among the most common shoulder problems [1]. RC disorders encompass a wide range of pathological conditions, which include bursitis, tendinitis, tendinosis, partial thickness tears and full-thickness tears [2]. In asymptomatic people with a mean age of 44.3 years, magnetic resonance imaging scans showed the prevalence of full-thickness tears was 10.3%, and in symptomatic patients, 40.8% [3]. Interestingly, poor posture has also been shown to be a predictor of RC disease. Tears were present in 65.8% of patients with kyphotic-lordotic postures, 54.3% with flat-back postures and 48.9% with sway-back postures; tears are present in only 2.9% of patients with ideal alignment [4]. An individual suffering from a RC injury may experience pain, tenderness, difficulty lifting their hand and an inability to carry out daily tasks due to the specific injury to their shoulder [5]. Young individuals who participate in sports are also more likely to sustain a RC injury. This injury affects quality of life and is quite common in older people. It happens during an upper extremity-related sporting activity and causes pain, weakness, soreness and restriction in shoulder movement [5]. There are two types of causes for this condition: non-traumatic and traumatic. Non-traumatic causes include muscle weakness and internal bony changes (osteoarthritis). Traumatic causes include genetic predisposition, extrinsic impingement and biomechanical imbalance from the RC structure, intrinsic degeneration from the muscles and tendon itself, and comorbidities [6].

Low-level laser therapy (LLLT), also known as photobiomodulation (PBM), has been used as a non-pharmacological alternative to treat painful musculoskeletal conditions [7]. PBM uses light-emitting diodes (LEDs) and other photo-emitting devices and is a minimally invasive approach used to treat a wide range of conditions. With wavelengths ranging from 400 to 1200 nm, the red-infrared portion of the electromagnetic spectrum contains the most researched phototherapies that aid inpatient rehabilitation [8, 9]. PBM reduces inflammation by improving microcirculation and stimulating angiogenesis while inhibiting inflammatory cells and cytokines and enhancing adenosine triphosphate synthesis [10]. Similarly, it is used to treat other musculoskeletal conditions, such as fibromyalgia patients, to enhance their quality of life and reduce pain. Also, it is used in addition to exercises to treat lumbar disk herniation [11].

Using infrared LEDs for PBM treatments has been shown to modify cellular and molecular metabolism, reducing pro-inflammatory cytokine levels (mRNA COX-2 and mRNA) and neutrophil and histiocytic counts in the treated area [12]. Given that there is limited research on PBM treatment for RC injuries and shoulder conditions, particularly in combination with exercise there is a need to evaluate the effectiveness of PBM along with exercise-based rehabilitation based on the pain and functional activity levels in patients with RC injuries. This study evaluated the effectiveness of PBM and exercise-based rehabilitation on pain and functional recovery in patients with RC pathology by assessing pain and range of motion (ROM) of affected shoulder joints.

2 Materials and Methods

2.3 Intervention

After assessing the patient's baseline NPRS and functional limitations, the participants were exposed to irradiation of PBM treatment for the duration of 10 days, after which the patients were started with structured exercise rehabilitation, which was prescribed for 4 weeks. PBM treatments were given with a cluster probe named Lasermed 2200-LT1372 manufactured by EME ITALY. While irradiation, the participants were instructed to expose the affected shoulder joint, and protective goggles were advised to be worn throughout the PBM session. The irradiation was given using the probe to the anterior joint line region and lateral aspect of the affected shoulder joint using the following parameters: A total of 19 diode LED cluster probes of 660 nm. The probe is equipped with a 10 × 660 nm LED that has an average power of 10 mW and an active area of 0.2 cm². The power density (irradiance) of the LEDs is 50 mW/cm². The probe laser was applied for 4 min at 156 Hz for each point as shown in Figure 1.

The exercise-based rehabilitation included, initially, submaximal isometric exercises for the muscles-deltoid, biceps, triceps and scapular stabilisers, followed by restoring full passive and active ROM exercises for the shoulder joint and progressive gentle strengthening of RC muscles [14].

3 Results

4 Discussion

The spectrum of injuries to the RC includes partial tears, tendinopathy, injury, and ultimately, full tears. We conducted a clinical study to assess the benefits of photobiomodulation and exercise-based therapy for RC pathologies. The study results show that the intervention resulted in a significant reduction in the NPRS level of patient pain intensity. The difference in pain outcome reported was five units on the NPRS from baseline and post-intervention. This indicates a 50% reduction in pain post-intervention using PBM therapy and exercises. Previous literature suggests that non-surgical physical therapy treatment of 6–12 weeks has been an effective treatment for full-thickness RC tears in 75% of patients up to 2 years of follow-up [3]. The surgical intervention will pose long-term structural and clinical success rates, present potential risks, lead to a longer duration of recovery, and require post-operative rehabilitation for satisfactory improvement [16].

A study by Scaldaferri Martins et al. showed the improvement in ROM, pain, strength and quality of life in individuals with RC retinopathy post-PBM intervention, along with therapeutic ultrasound in 4 weeks [8]. Similarly, a PBM therapy of pulsed 890 nm, when given for 8 min in patients with shoulder pain due to subacromial syndrome, proved more effective in the improvement of pain and ROM than exercise therapy alone [17]. Another study by Eslamian et al. [18] found that incorporating PBM into a combination treatment of exercises, along with heat therapy, ultrasound and TENS, resulted in greater pain relief than the combination therapy alone in a group of 50 patients with RC tendinitis. Overall, multiple evidences determine the effect of PBM in reducing pain, improving ROM of the shoulder, and quality of life. Contradictorily, a few studies showed no change in ROM after PBM therapy, although pain was improved after a month's follow-up [19, 20].

A systematic review by Marco Castaldo et al. in 2023, also showed that the use of LLLT, in combination with therapeutic exercises, was effective in treating shoulder pathology. The review found that LLLT combined with therapeutic exercise resulted in a significant decrease in pain severity and improved shoulder function [21]. Similarly, Nicholas Tripodi et al. conducted a systematic review in 2021 that demonstrated the benefits of LLLT and red-infrared photobiomodulation on pain and function in tendinopathy. The review found that PBM is increasingly being used to treat musculoskeletal disorders and that adjunctive exercise-adjunctive treatment with PBM resulted in reduced pain intensity and improved function and quality of life in patients with tendinopathies [19]. However, the effectiveness of PBM treatment in terms of biomechanical pathways requires further investigation.

Pain results from a stimulus that triggers the rapid propagation of action potentials along a nerve cell. This propagation is caused by the expulsion of positively charged sodium ions (Na+) and the influx of potassium (K+) ions into the nerve cell. The absorption of PBM by nerve cell receptors within the bilipid cellular membrane potentially holds significant potential for pain management. Lipids absorb best between 905 and 910 nm in wavelengths [12]. Upon absorption, the light generated by PBM therapy initiates a series of physiological effects that increase the permeability of the cellular membrane. This mechanism facilitates the reabsorption of Na+ ions into the cell and the removal of K+ ions, thereby maintaining the equilibrium of the sodium-potassium pump. This action effectively eliminates the pain signal at its origin, rendering PBM therapy a viable therapeutic option [12]. Exercise training regimens can also be made more effective with PBM. Thus, it should come as no surprise that PBM can aid in the healing of muscle injuries as well as lessen discomfort and soreness in the muscles following strenuous exercise. Numerous studies conducted on animals have examined indicators of oxidative stress and inflammation in muscle tissue taken from animals that have been sacrificed [12].

A recent study conducted by Martins et al. in 2022, analysed pain relief and functional recovery in patients with RC tendinopathy through therapeutic ultrasound and PBM. The study was a randomised controlled trial and compared the effectiveness of different treatments. The results of the study suggest that adding infrared and red LED treatments to ultrasound can improve the quality of life, reduce pain intensity, increase shoulder ROM, and enhance muscle strength for patients suffering from RC tendinopathy. The researchers concluded that infrared LED treatments could be a promising therapy for clinical practice [8, 22].

The major limitation of our study was the smaller sample size and the lack of a control group. Hence, future research can be recommended on a randomised controlled trial in evaluating the effect of PBM alone, which can provide clarity on the independent advantages of PBM in shoulder pathology and various musculoskeletal conditions. In conclusion, the integration of PBM therapy with exercise-based rehabilitation demonstrated a substantial improvement in pain reduction and improved ROM in the shoulder joint, as indicated by the results, and exercise-based rehabilitation shows promising results in improved functional activity in clinical practice.

Author Contributions

G. Arun Maiya: conceptualization. Esha Arora, Praveen Arany, Rene Jean Bensadoun, Nicolette Nadene Houreld and Liisa Laakso: methodology, writing – review and editing. G. Arun Maiya: formal analysis and investigation. Anupama Harihar and Grace Maria Joseph: writing – manuscript draft preparation. Anupama Harihar and Grace Maria Joseph: exercise-based rehabilitation. G. Arun Maiya: supervision. All authors contributed equally to the present review.

Conflicts of Interest

The authors declare no conflicts of interest.