Table 2.
Common OA behavioral tests, typical time commitment for the assay, and the relationship between these behaviors and common OA symptoms.
| Behavioral assay | Time commitment | Risks and concerns | Relation to human OA symptoms |
|---|---|---|---|
| Static weight bearing (incapacitance meter) | 5–10 minutes per animal | Little risk of injury; the enclosures and awkward handling postures may be stressful for the animal | Weight bearing during stance |
| Gait analysis | 20–30 minutes per animal | For overground testing, there is minimal injury risk, and this risk increases for treadmill testing; stress considerations include exposure to bright lights in some systems, prompting motion by the experiment (for non-voluntary exploration), and exposure to a treadmill (for treadmill testing). | Gait characteristics (though quadrupedal gait varies from that of bipedal humans) |
| Motor coordination (Rotorod) | 30–60 minutes for four animals | Some risk to the animal, as the endpoint of the assay is often falling from the rotating rod treadmill; the assay is stressful for the animal, as the animal is trying to stay on a rotating rod | A direct corollary to human symptoms of OA is unknown, though the assay measures sensorimotor coordination in rodents |
| Open field and LABORAS test | 12–24 hours per animal, often requiring individual animal housing | Little risk of injury; the enclosures may be stressful for the animal, as the arena may be unfamiliar to the animal; rodents typically live in colonies, and individual housing can be stressful for a rodent | Spontaneous activity |
| Mechanical allodynia (Von Frey test) | 30–60 minutes for 6–12 animals (depending on cage setup) | Little risk of injury. The enclosures may be stressful for the animal; moreover, the grate and wire floors may affect the animals’ behavior | Heightened sensitivity to light touch |
| Thermal hyperalgesia (Hargreaves’ method, hot plate, and/or tail flick test) | 5–10 minutes per animal | Risks of injury include minor burns and soreness; these assays distinctly cause pain in the animal, and thus are stressful for the animal; moreover, the enclosures for these tests can affect the animals’ behavior | Heightened sensitivity to heat |