Domestic cats (and all wild cats bar the cheetah, flat-headed cat and serval – but see last paragraph) are known for their ‘retractable’ claws. All the experts say it online but I disagree with them. To describe the claws as retractile or retractable misleads the way the tendons and muscles work.
The default position or position of rest for a domestic cat’s claws is retracted, which lifts them off the ground to a large extent.
The cat has to make a positive decision to extend the claws so that they become visible and start fully functioning. In a strict sense this means the claws are protrusible or protractile not retractile or retractable.
The difference between protractile and retractile is important in this instance. If the claws were retractable the cat would have to take positive steps and use his muscles to retract his claws for hours on end. This would be impractical and a waste of energy as the claws are normal tucked away. They are used for emergencies, stretching and when scratching, for instance. And, importantly, when a cat uses therefore paws to restrain prey. Cats clasp their prey animals using the claws on the toes of the forelegs. They are the only species of Carnivora which do this. They are well-known for their sharp claws.
Because the claws are retracted when at rest, they maintain their sharpness like a sword in a scabbard. Cat owners know this when scratched. It seems to me that in the rest position the relaxed muscle naturally pulls on the tendon which retracts the claw. No effort is needed.
In other words, use the words of Fiona Sunquist, “claw retraction is passive”. The claws are held off the ground by a retractor ligament. When a cat wants to extend its claws, they contract the dorsal and ventral muscles of the toe causing the ligament to stretch and the claws to protrude.
The claws of indoor/outdoor cats are usually less sharp on the forepaws because they are used often and come into contact with the ground and other objects frequently. As a result, they become slightly blunted or simply slightly less sharp. Indoor cats rest more which means there is less opportunity for the forepaws in particular to be blunted by day-to-day use.
It is worse for elderly cats. Their claws can grow too long and into their paw pads causing harm and pain. Cat guardians need to inspect the paw pads of elderly cats regularly and trim them when necessary.
Postscript: in the first paragraph I mentioned that the cheetah, serval and flat-headed are described as having non-retractable claws but it should be noted that they have the same claw retraction mechanism as other cat species. The difference is that their claws protrude beyond the fur. Also, the cheetah’s claws lack the sheaths that cover the claws of other cat species. Cheetahs rely upon their claws to twist and turn when running at high speed when chasing prey. That’s why they protrude more. They need them to improve their survival.
This is an opportune moment to briefly discuss declawing. A lot of people still think of the declawing operation as removing the claws of a cat because that is what the word means. The word describes that operation but it is highly misleading. It is actually the removal of the last phalange of the toe attached to which is the claw. It is an amputation times 10 because there are five toes on each paw. The claw grows from the last bone of the toe which is anchored by tendons. Remember that the claw is made of keratin, a hard protein, but the inner part of the claw is a form of modified skin called the dermis.
SOME MORE ON CAT CLAWS: