06/08/2026
Puppy Growth Plates: What Every Owner Should Know:
Growth plates are one of the most important, and most vulnerable, parts of your puppy's development. Understanding them can help prevent lifelong joint and bone problems.
1. What Are Growth Plates?
Growth plates, or physes, are soft areas of cartilage near the ends of long bones.
In a puppy, bone doesn't start as solid bone. New bone cells are made inside these cartilage plates, which allows the bone to lengthen. Think of them as the construction zones for the skeleton.
Once the puppy has reached its adult size, hormones - primarily estrogen and testosterone during puberty - signal the plates to stop producing new tissue. The cartilage then hardens and is replaced by solid bone. We call that "closing" or "fusing."
They are much softer than the rest of the bone, so they are more prone to injury and fracturing.
2. Where Are They Located?
Puppies have growth plates in almost every long bone, but the most clinically important ones are:
Front legs:
Distal radius and ulna - just above the wrist / carpus
Proximal humerus - near the shoulder
Distal humerus - near the elbow
Back legs:
Distal femur - just above the stifle / knee
Proximal and distal tibia - just below the knee and just above the hock
Proximal and distal fibula - runs alongside the tibia
Other places: Hip bones, pelvis, vertebrae, and jaw also have growth centers. Dogs under one year of age have growth plates located near the ends of the bones of the limbs.
An injury to any long-bone growth plate can affect how that limb grows.
3. When Do They Close?
Not all plates close at once. It happens from the bottom of the legs upward, and depends heavily on breed size:
Toy and Small breeds (under 25 lbs): 6 - 8 months
Medium breeds (25-50 lbs): 8 - 12 months
Large breeds (50-90 lbs): 12 - 18 months
Giant breeds (over 90 lbs): 18 - 24 months
Most of the rapid longitudinal growth happens between 4 to 8 months of age. After 8 months, little lengthening occurs, but the plates remain soft and open until they fully calcify.
4. Why Precautions Matter
While open, those plates are the weakest link in the skeleton. A force that would only sprain a ligament in an adult dog can fracture a puppy's growth plate.
5. Precautions to Prevent Injury
You don't need to keep a puppy in a bubble, but you do need to avoid repetitive impact and uncontrolled trauma until closure:
1. Limit forced, high-impact exercise: No long-distance running, jogging with you, bicycling alongside, or extended fetch on hard surfaces. The rule of thumb many vets use: 5 minutes of structured exercise per month of age, twice daily, until maturity.
2. Avoid repetitive jumping: No jumping in and out of SUVs, off high beds, over agility jumps, or off decks. Use ramps or lift giant breeds.
3. No hard, slippery floors for play: Puppies skidding and twisting at speed puts shear force on the distal radius/ulna and distal tibia. Use rugs and non-slip mats.
4. Keep roughhousing controlled: Most growth plate fractures are associated with minimal trauma, such as a fall, getting a leg caught, or simply rough-housing with another dog. Avoid wrestling with much larger adult dogs.
5. Watch weight and nutrition: Overfeeding and high-calcium or excessive protein puppy foods can cause rapid growth, which stresses plates. Feed a large-breed puppy formula if your puppy will be over 50 lbs as an adult, and keep them lean.
6. Delay intense sports: Agility, flyball and dock diving should wait until plates are closed - often 12-18 months for most active breeds, longer for giants. Ask your vet about a final growth-plate radiograph.
6. What Happens When There Is an Injury?
Growth plate injuries are called Salter-Harris fractures. They are graded I through V based on how the fracture crosses the plate, cartilage, and bone.
Signs:
Sudden lameness after a minor fall or play
Swelling around a joint, especially wrist or knee
Pain when touched, reluctance to bear weight
A limb that looks crooked or shorter after a few weeks
Consequences if not treated promptly:
Growth arrest: Part of the plate closes early while the rest keeps growing.
Angular deformity: If one side of a paired bone stops growing (very common with radius/ulna), the other bone continues and bends the leg. This causes bowed front legs or knock knees.
Short limb: The entire bone stops lengthening, leaving one leg shorter than the other.
Joint incongruity and early arthritis: Uneven growth means the joint surfaces no longer line up properly.
Even a mild injury can have lifelong effects because the plate controls future growth.
7. What Can Be Done?
This is always a veterinary emergency - ideally with a veterinarian within 24 hours.
Diagnosis: Physical exam plus x-rays of both the injured leg and the opposite leg for comparison. Sometimes a CT scan is needed.
Treatment depends on severity:
Mild, non-displaced (Salter I and II): Strict rest, splint or cast, anti-inflammatories and pain control, and repeated x-rays to ensure healing is straight.
Displaced or joint-involving: Surgery to realign the plate with tiny pins or wires, without crossing the plate itself if possible. The goal is to preserve as much growth potential as possible.
If deformity has already started: More complex corrective surgery, such as cutting the bone that is growing too fast or lengthening procedures, may be needed later. In severe cases where the plate has completely closed early, surgery is done to salvage joint function.
Aftercare: Restricted activity for 4-8 weeks, physical therapy, weight control, and joint supplements as recommended. Your vet will want follow-up x-rays at 2, 4, and 8 weeks to watch for premature closure.
Prognosis: Caught early and treated correctly, many puppies recover completely. Fractures near the end of the growth period or those caught late have a higher risk of deformity.
If your puppy suddenly goes lame after playing, even if it seems minor, don't adopt a "wait and see" approach. Keep them quiet, don't give human pain medication, and call your veterinarian.
For your specific puppy, ask your vet at the 6-month and 12-month check: "Do you think the growth plates are closed yet, and what activity level is safe now?" A quick x-ray is inexpensive compared to corrective orthopedic surgery.
EPS
This information is for education and does not replace veterinary advice. If you suspect a growth plate injury, contact your veterinarian promptly.
