Efficacy of Noninvasive 1060-nm Diode Laser for Medial Knee Fat Reduction

The advent of new technology such as noninvasive body-contouring devices has changed the business of surgical treatments and provided new options for addressing fat reduction. Lipolysis devices such as radiofrequency [4], cryolipolysis [5,6,7], ultrasound [8, 9], and lasers [1, 3, 10,11,12,13] are now being used worldwide as alternative procedures to remove fat in unwanted areas with a better safety profile compared with liposuction and other surgical procedures [1,2,3,4,5,6,7,8,9,10,11,12,13]. Each device has its own mechanism and efficacy profile [4,5,6,7,8,9,10,11,12].

A previous cryolipolysis study of 20 females with localized subcutaneous fat on arms or inner thighs showed significant circumference reduction at 3- and 6-month follow-up visits [5]. The efficacy was comparable to the present study, which also demonstrated reduction at 3 and 6 months post-treatment. Cryolipolysis works by inducing adipocyte apoptosis and inflammatory response using cold temperatures without damaging surrounding areas [5,6,7], while laser lipolysis generates controlled hyperthermia using a specific wavelength and optimal power in the subcutaneous layer and causes photothermal reaction that destroys adipocytes and stimulates inflammatory response [10, 13]. In the study by Decorato et al., hyperthermic laser lipolysis was comparable to cryolipolysis in average fat reduction at 3 and 6 months after treatment [13].

Previously conducted studies of 1060-nm diode laser showed significant reduction of localized subcutaneous fat on flanks [10] and abdomen [11]. The previous pilot study on the flanks demonstrated significant average fat reduction based on ultrasound images [10]. At 12 weeks after treatment, 96% (41/43) of subjects rated that they were satisfied with the treatment outcome [10]. Using the same device, Bass et al. showed a mean reduction in fat layer thickness of the abdomen from baseline at both 6 and 12 weeks after treatment [11]. At 12 weeks, 91% (31/34) of subjects were satisfied with the treatment [11].

In the present study, the results showed significant reduction of average knee circumference at 1 month (42.7 ± 4.2 cm), 3 months (41.9 ± 4.8 cm), 6 months (41.3 ± 4.4 cm) compared with baseline (p < 0.0001) (Table 3). Also, significant reduction in fat thickness of 2.0 ± 1.1 cm in axial plane and fat thickness of 2.0 ± 0.9 cm in sagittal plane at 1 month after treatment (p = 0.036, p = 0.001, respectively) and fat thickness of 1.5 ± 0.8 cm in axial plane and 1.6 ± 0.9 cm in sagittal plane at 6 months after treatment (p < 0.001) (Table 4) were also calculated based on ultrasound images. In our study, 17.7% of subjects at 3-month and 47.7% of subjects at 6-month follow-up visits rated > 75% improvement. The results of this study highlight that the 1060-nm diode laser is effective for subcutaneous fat reduction on medial knees. Considering that the laser device is kept in contact with the treated area using accessories (strap and frame) and the tapering of the temperature, the heat from the diode laser is localized to adipose tissue in the treatment area [10]. The patient satisfaction may be due to the medial knee fat reduction with smooth contour and lower rates of complications.

Similar to previously conducted studies, no severe adverse events were reported in our study [10, 11]. In a previous study using 924/975-nm diode laser, none of the patients presented persistent edema and pain. Of the 30 patients, 29 recommended the treatment [1]. In the study by Katz et al., the majority (83%) of reported events were mild and temporary. The subsequent events reported in the study by Katz were edema (resolved within 4–6 days), pain and bruising (resolved within 9–11 days), and subcutaneous nodules (resolved within 32–78 days) [10]. In addition, Bass and colleagues documented post-treatment tenderness as the most common adverse event [11]. Seventy-four percent of adverse events were reported as mild, 26% as moderate, and none as severe [11].

In our study, the average pain score recorded was 6.1 ± 1.0 (Table 1). All subjects reported mild tenderness and erythema immediately after treatment. No hypopigmentation, hyperpigmentation, scarring, fat dystrophy, infection, or paradoxical adipose hyperplasia were documented. The authors suggest that the best candidates and indications for noninvasive body contouring are patients who expect a mild to moderate result. Therefore, good candidates must be selected with realistic expectations.

In addition, our study showed that non-weight-gainers responded better to treatment. The average knee circumference of non-weight-gainers was reduced significantly at 1, 3, and 6 months after the single treatment (p < 0.001, p = 0.005, and p < 0.001, respectively) (Table 3). The average fat thickness of the non-weight-gainer group showed significant reduction at 6 months after treatment in both axial and sagittal plane (p < 0.001 and p < 0.001, respectively) (Table 4). Considering the current findings, the authors believe that diet control and regular exercise must be integrated with the subject’s lifestyle to maintain the treatment results and patient satisfaction.

To the best of our knowledge, this is the first study reporting the clinical efficacy and safety of a 1060-nm diode laser in the treatment of localized fat on medial knees. The limitations of the study include the small sample size, the lack of a comparative group, and short follow-up period. It would be prudent to conduct related studies with more subjects, additional treatment sessions, and longer follow-up to further examine the safety and efficacy of the 1060-nm diode laser on medial knees.