A puppy's legs change fast, and most of that change is healthy growth. The changes worth an early vet look are the ones involving alignment: a front leg that rolls so the puppy walks on the top of her toes instead of flat pads, a wrist that bends the wrong way, or two matching legs that stop matching each other.
What knuckling actually looks like
Knuckling means the toes fold under and the top of the foot contacts the ground, most often at the front wrist. You may first notice it on smooth floors, where the puppy's nails scrape or her paw flips under as she tires, then rights itself when she is fresh. Occasional clumsiness in a very young puppy is normal as coordination develops, but knuckling that appears repeatedly, lasts beyond a brief wobbly phase, or affects one leg more than the other is worth flagging. Check her standing still as well as moving: from the front, each wrist should sit in a straight column above its paw, not buckled forward or sagging toward the floor.
Comparing left and right, week by week
Uneven growth rarely announces itself in a single day; it creeps in as one limb angles outward, bows, or turns while its partner stays straight. Stand her squarely on a non-slip surface once a week and look from the front and the side, then take a phone photo from the same position so you are comparing pictures rather than memories. Watch for one elbow held away from the body, one paw consistently turned out, a difference in how the two front legs meet the ground, or a shoulder or wrist that looks larger on one side. Puppies who start skipping a leg, lagging on walks they used to enjoy, or bunny-hopping with the back legs are also telling you something has changed.
Growth plates, feeding, and why early matters
Young bones lengthen at growth plates near the joints, and those plates are softer and more vulnerable than adult bone. An injury to one plate, or growth that proceeds unevenly between paired bones in the forearm, can change the angle of the whole limb as the puppy keeps growing — which is why timing matters more in a puppy than in an adult dog. Feeding plays a background role too: oversupplementing a growing puppy, particularly a large-breed one, or pushing growth faster than the skeleton is ready for can add strain, so keep to a complete puppy diet appropriate to her size and raise any supplement ideas with the vet first.
What not to do at home
Do not splint, bandage, or brace a knuckling or uneven leg yourself, and do not start joint supplements or extra calcium on the strength of an internet photo that looks similar. A support placed on the wrong joint, or tightened around a growing limb, can worsen the very alignment you are worried about, and unnecessary calcium can disturb the balance a complete puppy food already provides. Rest her from slippery floors and rough play with bigger dogs while you wait for the appointment, note when you first saw the change, and bring the dated photos — that restraint plus good records helps the vet far more than a home fix.
Booking the early look
Make the appointment promptly if knuckling persists, if one limb visibly differs from the other, if a wrist or elbow looks swollen, or if she is lame for more than a day or two without an obvious minor cause. Growth problems are one area where a few weeks genuinely changes the options, because so much length is still to come. Storing her dated standing photos, weight checks, and the vet's growth notes together in her KinsLe Pet Passport means the change over time is documented in one packet the vet can review at a glance.