Purpose: Osteoarthritis (OA) is a whole organ joint disease with high prevalence in knee joint. Such morbidity can lead to functional disability. OA is characterized by cartilage degradation, abnormal subchondral bone remodeling and synovitis. Cross-link was suggested between subchondral bone and cartilage in the pathogenesis of OA. The restoration of subchondral bone integrity may be associated with retardation of cartilage degradation. Low level laser therapy (LLLT) at red to near infrared wavelength has been reported to be osteogenic and chondroprotective in numerous in-vitro experimentation. Structure, form and function are interrelated. The study aimed to investigate that LLLT may restore the integrity of cartilage, subchondral bone and improvement of gait function in vivo. LLLT exhibits a dose dependent treatment effect. The effectiveness of two exposure regimes on the mentioned outcomes will also be studied. Methods: Forty female Sprague-Dawley rats aged 3-month old were randomized into studied groups of non-operated control (CG), placebo LLLT (PG), 80-second LLLT (L80) and 800-second LLLT (L800). Anterior cruciate ligament transection (ACLT) was performed in the right knee joint of PG, L80 and L800 only and with 10-week free cage movement to establish OA changes. At 10 week post-ACLT, ten daily sessions of 80- and 800-second LLLT (50 mW, 820 nm) were given to L80 and L800, respectively on right knee joint for two weeks. At 12 week post-ACLT, all the rats were sacrificed after gait adaptation measurement using Catwalk system. Right proximal tibiae were then harvested for subchondral bone density and micro-architecture measurements using micro-computed tomography, cartilage morphology and biomechanical properties were evaluated using ultrasound microscopy and micro-indentation, respectively. Comparison among the groups for the outcome measurements were analysed by one-way ANOVA statistics. Results: Firstly, microCT study of proximal tibial epiphysis showed that apparent trabecular bone mineral density (atBMD), bone volume fraction (BV/TV), trabecular number (Tb.N), and trabecular thickness (Tb.Th) were significantly lower in the PG compared with CG (P < 0.05). The findings revealed that there could be abnormal subchondral bone remodeling which may be associated with the joint instability induced by ACLT. In contrast, treatment groups with 800-second LLLT or 80- second LLLT showed that atBMD, BV/TV, and Tb.Th were significantly greater than PG (P < 0.05). The results indicated that LLLT could restore the loss of subchondral bone mineral density and micro-architecture in ACLT induced knee OA. Secondly, morphology study showed that cartilage thickness in medial tibia was significantly increased in the L80 compared with PG (P < 0.05). However, cartilage roughness and cartilage integrated reflection coefficient in both medial and lateral tibia as well as cartilage thickness in lateral tibia did not show significant change either in the L80 or L800 groups compared with PG. Biomechanical properties of cartilage as revealed in its elastic modulus showed no significant different either in L80 or L800 groups compared with PG. These findings showed that LLLT could increase thickness of cartilage but no improvement of cartilage biomechanical property was found. Thirdly, the ACLT also brought about changes in gait adaptation. Mechanical allodynia during ambulation in OA animals was shown in the PG groups with significant decrease in the percent paw area and increase in the percent swing duration of the right hind limb (OA right knee) (P < 0.05). The findings showed that LLLT treatment could reduce the mechanical allodynia and restore the normal ambulation. Conclusions: Our results supported that LLLT could restore subchondral bone density and micro-architecture as well as cartilage thickness in the OA rat model. However, no effect of LLLT was observed in cartilage elastic modulus. These modifications may relate to the reduction of mechanical allodynia and normalization of gait function. (Figure presented).
Yip, K.-K., Leung, C.-P. M., Cheung, W.-H. L., & Lai, Y.-M. (2016). Effects of low level laser therapy: a study of status of cartilage, subchondral bone and gait adaptation in the rat anterior cruciate ligament transection model of osteoarthritis. Osteoarthritis and Cartilage, 24, S487–S488. https://doi.org/10.1016/j.joca.2016.01.893