Inner Salamander?

Recent research has suggested that the former view that adult humans cannot repair damaged cartilage is not quite true (https://www.theguardian.com/society/2019/oct/09/our-inner-salamander-could-help-treat-arthritis-study-finds ). It does seem possible to stimulate repair (a process that could be very useful in treating arthritis) and this is easier in the toes and fingers than in the knees and elbows. The authors speculate that this may a hangover of a process in animals like salamanders who can regrow appendages lost to predators. Re-growing a finger is easier for them than items closer to the body (which would make sense if the bulk of the amphibian escaped the attack). There could, however, be alternative suggestions. Cartilage may grow better at lower temperatures (as in the extremities) than in areas that are more internal?