CLINICAL RESEARCH – LIGHT THERAPY RESEARCH

DISCUSSION

This study shows the efficacy of phototherapy in DOA in late middle-aged and elderly patients. Patients treated with red or infrared light emitters reported more than 50% pain relief after 10 days of treatment. Pain relief continued for an average of 4 to 6 months after the treatment. Our results are similar to those reported by Trelles et al. 17 They studied the impact of infrared diode laser (860 nm, 60 mW, CW) on pain, inflammation, joint mobility, and treatment tolerance in patients with DOA. Their study showed significant improvement immediately after 4 weeks of twice weekly treatments and 4 months later.

The exact mechanism of pain reduction by phototherapy is not completely understood. Many investigators have observed an anti-inflammatory effect of phototherapy in studies conducted in patients with rheumatoid arthritis. 18-20 A recent histochemical study has shown a marked increase of prostaglandin I2 following phototherapy, and consequently inhibition of platelet aggregation and vasodilation. 21 Improvement of local circulation leads to reduction of edema and better oxygenation of tissues and thus may result in reduction of pain. Lack of Na-K-ATPase activity seems to increase nociceptive impulse transmission; an increase in Na-K-ATPase following phototherapy may be a factor in pain attenuation. 22 Thus, phototherapy could produce pain relief by one or a combination of these mechanisms: anti-inflammatory effect, circulation enhancement, and analgesic effect.

We observed the same degree of improvement in pain relief and functional ability in the red and infrared treated groups. Patients treated with placebo emitters did not report any changes in pain, except for a small (10%) and statistically insignificant ( P = 0.163 ) degree of pain relief reported in the affective component of the SF-MPQ.

The red and infrared treated groups showed significant improvement in functional disability, more than 40%, perhaps due to the reduction in pain intensity and possibly also contributed to by a direct effect of phototherapy on knee mobility. The placebo treated patients did not show significant functional improvement, and the observed slight improvement (7%) probably reflected a placebo effect (use of the emitters).

In conclusion, this study showed that short-time application of phototherapy is effective in pain relief and in improvement of functional ability in elderly patients with DOA. Thus, phototherapy can be an important adjunct in treatment of this disease, especially in patients with adverse side effects to drug treatment. Our personal experience suggests that phototherapy can be used conjointly with analgesics to reduce their dosage. These encouraging results might prompt further, long-term studies to validate this treatment and to establish more detailed indications for the use of phototherapy in DOA.

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