Background information: Intra-articular injection of monosodium iodoacetate (MIA) into the knee joint is a well-characterized preclinical model of osteoarthritis, manifested by articular inflammation, decreased weight bearing on the injured limb, movement-evoked pain, and referred pain (hypersensitivity to acute application of noxious (hyperalgesia) and non-noxious (allodynia) stimuli to the hind paw).

Animals: Wistar rats.

Efficacy test: The efficacy of drugs (systemic or topical administration) can be evaluated after acute administration on day 14 after MIA injection (acute analgesic effect), or after repeated treatment in a preventive or curative protocol (disease-modifying effect, analgesic potentiation or tolerance). Efficacy evaluation of drug combinations is also possible, including isobolographic analysis of the interaction.

Assessments: Mechanical allodynia is evaluated by measuring hind paw withdrawal threshold (g) in response to mechanical (von Frey test) stimulation. Additional readouts (weight bearing, gait analysis) can also be evaluated.

Positive control: opiods (acute analgesic efficacy, analgesic tolerance)

Criteria for significance: ANOVA followed by Tukey’s test is applied for comparison between the vehicle and treatment groups. Significant activity is considered at the P<0.05 level.

Turnaround time: xx Days.