Many plants have been introduced in Iranian traditional medicine for treatment of different joint problems including knee pain. Topical application of the mixture of Lawsonia inermis L. leaves (Henna) with aqueous extract of Ricinus communis L. leaves have been mentioned to have significant effects on reducing knee pain. The present study was designed to evaluate the analgesic and anti-inflammatory effects of the mixture of these two herbs in male rats.
We induced knee osteoarthritis as a model of chronic pain by intra-articular injection of mono sodium iodoacetate (MIA). Mechanical allodynia, hotplate latency test, spontaneous movements and gait analysis were used for the evaluation of analgesic activity. Anti-inflammatory activity was evaluated by measuring the diameter and the volume of the injected paw compared to contralateral paw. These tests were monitored at days 1, 3, 7, 14 and 21 of MIA administration. Histopathological evaluations were also used to assess the efficacy of the treatment on inflammation and lesions in knee tissue. In all tests, diclofenac topical gel was used as a positive control. The herbal extracts, their mixture, and vehicle or diclofenac gel were administered daily for 14 days by topical route.
The mixture of these two extracts significantly reduced the knee joint width and volume of the injected paws and also improved foot prints in gait analysis after 3 days of MIA injection. Analysis of mechanical allodynia (after 21 days), hotplate latency test (after 10 days), spontaneous movements (after 7 days) and in positive control group (after 3 days in all tests and in mechanical allodynia after 14 days) compared to the vehicle group, showed significant effects. Topical usage of the selected formulation made significant histopathological changes on the knee of the rats. Compared to the vehicle group, the tests and diclofenac groups showed less reactions characterized by negligible edema and a few scattered inflammatory lymphoid cells.
The present findings showed that the present formulation not only was able to mitigate pain and inflammation in the paws but also made significant histopathological changes on the knee of the rats. Further studies are necessary to confirm the effect of the formulation.