Chapter 7 Rehabilitation Physical Modalities 157The literature also supports using LLLT to
address myofascial pain (Rayegani et al., 2011;
Taheri et al., 2016), neck pain (Chow et al.,
2009), low back pain (Huang et al., 2015), oste
oarthritis (Youssef et al., 2016), and rheumatoid
arthritis (Alves et al., 2013a). Several studies
noted reduced need for analgesic medications
following treatment with LLLT (Cavalcanti
et al., 2016; Khalighi et al., 2016). LLLT has also
been shown to reduce discomfort through
stimulation of acupuncture or muscle trigger
points (Snyder‐Mackler et al., 1989; Al Rashoud
et al., 2014; Erthal et al., 2016).
While the mechanisms by which LLLT affects
pain are still not fully understood, it is believed
that LLLT application may cause enhancement
of peripheral endogenous opioid production
(Hagiwara et al., 2007), an inhibition of action
potentials by the peripheral nerve endings of
nociceptors (Cotler et al., 2015), and a reduction
of nociceptor activation at the spinal level
(Nadur‐Andrade et al., 2016).
It is important to note that the effects of LLLT
are dependent on multiple factors including
dose, wavelength, single versus combination of
wavelength, depth of target tissue, and frequency
of treatment. There are laser studies that do not
have satisfactory outcomes on healing or pain
management with laser therapy, but when
closely examined, these studies may not have
appropriate parameters.
Therapeutic effects on tissue healing
and protection
The absorption of light energy by chromo
phores causes a number of biological effects
including increased ATP production and
changes in cell membrane permeability (Karu,
1988; Karu et al., 1995; Vartika et al., 2015), pro
moting improved cellular function. LLLT has
been shown to facilitate collagen synthesis
(Tatmatsu‐Rocha et al., 2016) with a greater col
lagen content observed in treated wounds
(Guerra Fda et al., 2013; Ranjbar & Takhtfooladi,
2016). Increased growth factor release (Saygun
et al., 2012; Martignago et al., 2015) and stimula
tion of fibroblast development (Frozanfar et al.,
2013; Rathnakar et al., 2016) also occurs, with a
resultant increase in wound tensile strength
(Vasilenko et al., 2010; Suzuki & Takakuda,
2016). Additionally, LLLT increases angiogenesis
(de Medeiros et al., 2017) leading to the forma
tion of new capillaries in injured tissues (Ihsan,
2005; Corazza et al., 2007; Wagner et al., 2016),
and more rapid wound healing in general
(Hopkins et al., 2004; da Silva et al., 2010; Lima
et al., 2017). A 2016 study by Mathur and col
leagues demonstrated that, even in challenging
wound environments such as diabetic foot
ulcers, the addition of LLLT to conventional
therapy promotes a more rapid reduction in
wound size and higher amounts of granulation
tissue in as little as 2 weeks compared with
patients who received conventional wound care
only (Mathur et al., 2017). Furthermore, LLLT
may be useful in the treatment of infected
wounds as shown by a significant reduction in
bacterial growth (Ranjbar & Takhtfooladi, 2016).
When considering specific tissue types, LLLT
has shown positive effect toward the healing of
connective tissues, such as ligament (Fung et al.,
2002) and tendon (de Jesus et al., 2014) as well
as skin. A 2016 study showed that LLLT pro
motes healing of tendinopathy as evidenced by
increased production of collagen (Marques et al.,
2016). It can also accelerate skeletal muscle repair
(Assis et al., 2016; De Marchi et al., 2017), assist in
the recovery of articular tissues following injury
(Alves et al., 2014; Lemos et al., 2016), improve
cartilage thickeness in patients with osteoarthri
tis (OA) (S et al., 2016), protect articular cartilage
(Bublitz et al., 2014; Assis et al., 2016; Tomazoni
et al., 2017), hasten the formation of new bone
tissue (de Almeida et al., 2016; Tim et al., 2016),
promote better bone health in animals with spi
nal cord injury (Medalha et al., 2016), and pro
mote functional recovery of nerves (Gigo‐Benato
et al., 2004; Rochkind et al., 2009; Takhtfooladi
et al., 2015; Ziago et al., 2017). Indeed, there is evi
dence that LLLT reduces inflammation and pro
motes functional recovery following spinal cord
injury in a rat model (Veronez et al., 2017).
Specific to the canine patient, LLLT may pro
mote CNS healing as demonstrated by a more
rapid return to ambulatory status following
hemilaminectomy to address intervertebral disc
disease (IVDD) (Draper et al., 2012).Therapeutic effects on tissue flexibility
and joint ROM
Likely through a combination of pain reduction
and decreased inflammation, LLLT can increase