Background. In patients with chronic knee pain and degenerative gonarthrosis, a wide range of physical agents are used, along with local application of non-steroid anti-inflammatory and analgesic drugs in gel or cream form. The evaluation of the clinical and functional status associated with changes in muscle tension and blood flow in the knee region can be facilitated by thermovisual tests, which measure the intensity of infrared radiation to determine skin temperature differences. Material and methods. 99 successive patients diagnosed with gonarthrosis and knee pain persisting > 6 weeks were enrolled. All patients were randomly assigned to one of three groups: Group A (n=32), who received laser biostimulation; Group B (n=35), who received the same laser procedures, and were also instructed to use sodium diclofenac (Voltaren gel) as an inunction on the affected joint; and Group C (n=32), a comparison group. We evaluated pain intensity using the VAS scale, and measured temperature distribution with thermograms performed twice in all patients, before and after treatment. Results. Significant reductions in pain intensity and frequency were observed in groups A and B, but Group B showed significantly greater improvement. In both experimental groups, thermograms showed normalization of temperature distribution. Conclusions. An improper temperature distribution along the lower extremity and around the patella was observed in patients with knee pain syndrome. The application of laser biostimulation in gonarthrosis produces temperature normalization in the irradiated tissues and reduced pain symptoms, which was more pronounced when combined with externally applied sodium diclofenac gel.