Table 4 Different animal models for cartilage rejuvenation or repair

Rabbit

Intramuscular injection of Xylazine hydrochloride (5 mg/kg BW) and ketamine hydrochloride (50 mg/kg BW)

3 mm diameter critical size defect at shoulder or knee, depth 0.2–0.5 mm at the chondral or osteochondral site (Fig. 1f)

Low cost, easy to handle, and house, but different from humans in respect of biomechanics due to their different hopping and walking pattern

Sheep/Goat

General anesthesia with intramuscular injection of Xylazine hydrochloride @ 0.1–0.2 mg/kg BW

Knee joint surgically exposed and 6–7 mm circular critical defect is to be created with 0.4–1.5 mm depth at chondral/osteochondral site

Easy to rare, handle and have close anatomical similarity with humans but knee contact areas are different, hence this must be considered

Dog

General anesthesia using preanesthetic atropine sulphate @0.04 mg/kg BW SC, after 10 min xylazine 1–2 mg/kg BW IM. Maintenance by ketamine @5–10 mg/ kg BW IV and diazepam 0.5 mg/ kg BW slow IV

Surgically created 4 mm diameter circular critical size defect of 0.95–1.3 mm depth at the chondral/osteochondral site of Knee, shoulder, elbow, hip or ankle joint

They are a good model for cartilage repair as they can be trained for treadmill walking, swimming, etc. But, disadvantages are there. Firstly, ethical issues in several countries, moreover canine cartilage is thinner compared to human and anatomical difference exists in the knee joint