Table 2.

Outcome options in mouse models of osteoarthritis

Test name	Techniques	Kind of assessment	Output	Specific equipment required
Static measurement
Von Frey filament testing	Calibrated nylon filaments of various thickness (and applied force) are pressed against the skin of the plantar surface of the paw in ascending order of force	Stimulus- evoked pain-like behavior Mechanical stimuli - Tactile allodynia The most commonly used test	Latency to paw withdrawal and Force exerted are recorded	Yes
Knee extension test	Apply a knee extension on both the intact and affected knee or Passive extension range of the operated knee joint under anesthesia	Stimulus-evoked pain-like behavior	Number of vocalizations evoked in 5 extensions	None
Hotplate	Mouse placed on hotplate. A cutoff latency has been determined to avoid lesions	Stimulus-evoked pain-like behavior Heat stimuli- thermal sensitivity	Latency of paw withdrawal	Yes
Righting ability	Mouse placed on its back	Neuromuscular screening	Latency to regain its footing	None
Cotton swab test	Bringing a cotton swab into contact with eyelashes, pinna, and whiskers	Stimulus-evoked pain-like behavior Neuromuscular screening	Withdrawal or twitching response	None
Spontaneous activity
Spontaneous cage activity	One by one the cages must be laid out in a specific platform	Spontaneous pain behavior Nonstimulus evoked pain Activity	Vibrations evoked by animal movements	Yes
Open field analysis	Experiment is performed in a clear chamber and mice can freely explore	Spontaneous pain behavior Nonstimulus evoked pain Locomotor analysis	Paw print assessment Distance traveled, average walking speed, rest time, rearing	Yes
Gait analysis	Mouse is placed in a specific cage equipped with a fluorescent tube and a glass plate allowing an automated quantitative gait analysis	Nonstimulus evoked pain Gait analysis Indirect nociception	Intensity of the paw contact area, velocity, stride frequency, length, symmetry, step width	Yes
Dynamic weight bearing system	Mouse placed is a specific cage. This method is a computerized capacitance meter (similar to gait analysis)	Nonstimulus evoked pain Weight-bearing deficits Indirect nociception	Body weight redistribution to a portion of the paw surface	Yes
Voluntary wheel running	Mouse placed is a specific cage with free access to stainless steel activity wheels. The wheel is connected to a computer that automatically record data	Nonstimulus evoked pain Activity	Distance traveled in the wheel	Yes
Burrowing analysis	Mouse placed is a specific cage equipped with steel tubes (32 cm in length and 10 cm in diameter) and quartz sand in Plexiglas cages (600 · 340x200 mm)	Nonstimulus evoked pain Activity	Amount of sand burrowed	Yes
Digital video recordings	Mouse placed is a specific cage according to the tool	Nonstimulus evoked pain Or Evoked pain	Scale of pain or specific outcome	Yes
Digital ventilated cage system	Nondisrupting capacitive-based technique: records spontaneous activity 24/7, during both light and dark phases directly from the home cage rack	Spontaneous pain behavior Nonstimulus evoked pain Activity-behavior	Distance walked, average speed, occupation front, occupation rear, activation density. Animal locomotion index, animal tracking distance, animal tracking speed, animal running wheel distance and speed or rotation	Yes
Challenged activity
Rotarod test	Gradual and continued acceleration of a rotating rod onto which mice are placed	Motor coordination Indirect nociception	Rotarod latency: riding time and speed with a maximum cut off.	Yes
Hind limb and fore grip strength	Mouse placed over a base plate in front of a connected grasping tool	Muscle strength of limbs	Peak force, time resistance	Yes
Wire hang analysis	Suspension of the mouse on the wire and start the time	Muscle strength of limbs: muscle function and coordination	Latency to fall gripping	None (self -constructed)

Pain cannot be directly measured in rodents, so methods have been developed to quantify “pain-like” behaviors. The clinical assessment of mice should be tested both before and after the intervention (induced-OA ± administration of treatment) to take into account the habituation and establish a baseline to compare against.