What is the Logic Behind Not Exercising Puppies Until the Growth Plates are Closed?

Over the years, many breeders, trainers, and owners have said that puppies should not be exercised until the growth plates are closed. I have been asked to radiograph 12-month-old dogs to make sure their growth plates are closed. Recently, a well-regarded colleague told me that he had an owner that had signed a contract with the breeder that she would not take the puppy outside until the growth plates were closed! What?

Warning: This a long post. If you want to skip the science, go right to the summary. But I think you’ll find the science interesting. Details count when it comes to our puppies.

I was fortunate enough to see a pack of African Wild dogs a couple years ago on a safari in South Africa. It occurred to me that these dogs, including young pups were running, playing, tumbling and having a good time. Wonder if they waited until their growth plates were closed? Then I thought about all of the children that are involved in sports – soccer, basketball, football, baseball, softball, etc. Do their physicians and the parents do radiographs to assess growth plate status? I asked a physician friend of mine if there were any concerns about the growth plates of children doing reasonable amounts of exercise and sports. He knew of no common conditions or concerns, except not to do heavy weightlifting.

So back to the original thought of how did these recommendations come to be, and what does the science say? Maybe the recommendations to not exercise puppies are so that orthopedic conditions are not exposed, and the onset of arthritis and lameness due to these conditions is delayed until warranties expire. Or is there science to support such recommendations?

First, what is a growth plate? The growth plate, or physis, is the region of bone in a growing dog that results in lengthening of a bone, and therefore the limb. In essence, this is how dogs grow. Growth plates close at a predictable age, based on the size of the dog. Toy and miniature breeds generally have closure of growth plates at 6-8 months of age, while some growth plates of large or giant breeds of dogs may remain open until 14-16 months of age. Keep in mind that most growth in height is completed before the growth plates completely close.

Certainly fractures involving the growth plates occur, but these are associated with some sort of trauma, such as being hit by a car, jumping from a high height, or being run into by another dog. It is true that this type of trauma often results in premature closure of the growth plates, shortening of the limb, and sometimes angulation of the limb if the injury involves a part of the limb with two bones, such as the radius and ulna (the forearm of the dog), and the growth plate of one bone closes (usually the ulna) while the other continues to grow (usually the radius). However, in good conscience, I cannot recall a case of premature closure of growth plates based on exercise or vigorous training.

What about exercise and risk to joints? One study done in Norway evaluated exercise-related risk factors associated with development of radiographic hip dysplasia in Newfoundlands, Labrador Retrievers, Leonbergers, and Irish Wolfhounds. (Krontveit, et al. Am J Vet Res 2012;73:838–846). They suggested that there was an increased incidence of hip dysplasia in puppies climbing stairs from birth to 3 months of age. They further suggested that off-leash activity had a protective effect against hip dysplasia. Another study evaluated diet, exercise, and weight as risk factors in hip dysplasia and elbow arthritis in Labrador retrievers (Sallander et al, J Nutr 2006, 136:2050S–2052S). Ad libitum feeding, although in relatively few dogs, was highly associated with these joint conditions. Running after balls and sticks thrown by the owner were also identified as risk factors. Slater et al (Am J Vet Res.1992, 53:2119-24) also suggested that prolonged or jarring activity, such as running after a ball or a stick in a high speed, might lead to the development of osteochondritis dissecans (OCD), a condition found in large and giant breeds of dogs that results in a thickened area of cartilage in joints, such as the shoulder, and a weak area of cartilage that may break off as a large flap. Others have suggested that there may be some type of traumatic event, such as jumping, that results in trauma to the bone under the joint cartilage, resulting in a residual thickened area of cartilage that then may break off. However, the breed, genetics, and diet seem to have a larger contribution the development of OCD.

So, jarring, high impact activity may be risk factors for some joint conditions. But keep in mind that none of these studies fully considered the genetic component of the dogs. Further, there is very good evidence that being overweight as a puppy in more likely to contribute to joint disease. Nevertheless, avoiding jarring, high concussive activity during the formative months seems to be a prudent recommendation.

What about regular exercise? Here is where things get interesting (further details may be found in the chapter on Responses of Musculoskeletal Tissues to Disuse and Remobilization in our Canine Rehabilitation and Physical Therapy book). And keep in mind that the described studies involved breeds of dogs with low risk of elbow dysplasia, hip dysplasia, or osteochondritis dissecans. Exercise places demands on joint cartilage, which becomes conditioned to transmit the stresses to which it is subjected. Mild to moderate levels of running in dogs may stimulate adaptation. Most studies of moderate running indicate no injury to articular cartilage, assuming there are no abnormal biomechanical stresses acting on the joints, such as hip or elbow dysplasia or rupture of the cranial cruciate ligament (exercise certainly accelerates the development of arthritis in abnormal joints).

Young beagle dogs jogging 4 km/d (2.5 miles), at a speed of 4 km/h (2.5 mph) at a 15-degree incline on a treadmill for 15 weeks had no damage to cartilage and a 6% increase in cartilage stiffness and an 11% increase in cartilage thickness, all positive changes. Jogging 20 km/d (12 miles) on a treadmill for 15 weeks did not result in further changes. Skeletally immature dogs subjected to 15 weeks of jogging at a rate of 40 km/d (24 miles per day!!!) had no change in cartilage content. However, running 20 km/d for nearly 1 yearresulted in a 6% reduction in cartilage thickness of the medial femoral condyle, with an 11% reduction in proteoglycan content (the part of the cartilage that gives it stiffness and wear resistance). In similar studies of running 40 km/d, the effects of training for 1 year on young canine articular cartilage found that there was no visible cartilage damage, but there was some softening of the cartilage. But these are all huge distances. Think about running a marathon or half marathon 5 days a week for a year! Like Forrest Gump, just keep on running for no particular reason!

Strenuous training in older dogs may result in deleterious changes. Running aged dogs on a treadmill at 9.6-12.8 km/h (6-7.5 mph) for 1 h/d, 6 d/week for 8 months led to cartilage degradation in the femoral head, part of the hip joint. Proteoglycan content was decreased, there was destruction of collagen fibrils, and erosion and fibrillation of the cartilage surface. But again, this is a lot of exercise.

What about lifelong low-impact exercise? In yet another study, dogs were exercised on a treadmill at 3 km/h (1.9 mph) for 75 min, 5 d/wk for 527 weeks (10 years!) while wearing jackets so that the total weight carried was 130% of body weight. There were no ligament, meniscal, or cartilage injuries, or osteophytes found. Biochemical, cartilage thickness, and biomechanical properties were not affected by training. These results suggest that a lifetime of relatively low-impact weight-bearing exercise in dogs with normal joints does not cause damage to joint cartilage.

Summary

So what can we conclude about exercising puppies? The most important thing is that puppies should be free of hip and elbow dysplasia, and genetic tendencies to conditions such as osteochondritis dissecans. The most important environmental issue is to keep puppies thin and not let them get overweight. High impact exercise (such as jumping from heights or sharp turns) should be avoided until maturity and a period of adequate conditioning, agility and strength training. There is no evidence that normal exercise causes damage to growth plates of puppies. In fact, jogging exercise (such as on a treadmill) appears to be beneficial to normal joints. It takes a lot of exercise to cause damage to joint cartilage. Jogging an hour per day seems to be beneficial to joint cartilage. But high speed running for long distances (12-24 miles per day) may eventually result in deleterious changes to cartilage. Dogs are built to run. Further, normal puppy play helps them to develop muscle, ligament, tendon, bone, and cartilage strength as well as coordination and proprioception. Maybe that’s why African wild dogs run and play so much!

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Noora Waltari asked for the references about the exercising dogs, and many of the rest of you may be interested as well. It's interesting that a lot of the exercise and sports science information for people was obtained from dogs, but of course there are many differences between people and dogs. But much of the original literature was published in journals pertaining to people, so they are not as well know in veterinary circles. As mentioned, the studies are summarized in the Responses of Musculoskeletal Tissues to Disuse and Remobilization chapter in our Canine Rehabilitation and Physical Therapy book. But here are the pertinent cited references from that chapter. Enjoy!

Kiviranta I, Jurvelin J, Tammi M, et al: Weight bearing controls glycosaminoglycan concentration and articular cartilage thickness in the knee joints of young beagle dogs, Arthritis Rheum 30:801-809, 1987.

Jurvelin J, Kiviranta I, Saamanen AM, et al: Partial restora- tion of immobilization-induced softening of canine articular cartilage after remobilization of the knee (stifle) joint, J Orthop Res 7:352-358, 1989.

Palmoski MJ, Brandt KD: Effects of static and cyclic com- pressive loading on articular cartilage plugs in vitro, Arthri- tis Rheum 27:675-681, 1984.

Radin EL, Martin RB, Burr DB, et al: Effects of mechanical loading on the tissues of the rabbit knee, J Orthop Res 2:221-234, 1984.

Donohue JM, Buss D, Oegema TR, et al: The effects of indirect blunt trauma on adult articular cartilage, J Bone Joint Surg Am 65:948-957, 1983.

Wang J: Response of calcified cartilage to blunt trauma. Chinese J Sports Med (Beijing) 9:65-66, 1990.

Hallett MB, Andrish JT: Effects of exercise on articular cartilage, Sports Med Arthroscopy Rev 2:29-37, 1994.

Jurvelin J, Kiviranta I, Tammi M, et al: Effect of physical exercise on indentation stiffness of articular cartilage in the canine knee, Int J Sports Med 7:106-110, 1986.

Kiviranta I, Tammi M, Jurvelin J, et al: Moderate running exercise augments glycosaminoglycans and thickness of articular cartilage in the knee joint of young beagle dogs, J Orthop Res 6:188-195, 1988.

Jurvelin J, Kiviranta I, Saamanen AM, et al: Indentation stiffness of young canine knee articular cartilage—influence of strenuous joint loading, J Biomech 23:1239-1246, 1990.

Kiviranta I, Tammi M, Jurvelin J, et al: Articular cartilage thickness and glycosaminoglycan distribution in the canine knee joint after strenuous running exercise, Clin Orthop 283:302-308, 1992.

Arokoski J, Jurvelin J, Kiviranta I, et al: Softening of the lateral condyle articular cartilage in the canine knee joint after long distance (up to 40 km/day) running training lasting one year, Int J Sports Med 15:254-260, 1994.

Arokoski J, Kiviranta I, Jurvelin J, et al: Long-distance running causes site-dependent decrease of cartilage glycos- aminoglycan content in the knee joints of beagle dogs, Arthritis Rheum 36:1451-1459, 1993.

Oettmeier R, Arokoski J, Roth AJ, et al: Quantitative study of articular cartilage and subchondral bone remodeling in the knee joint of dogs after strenuous running training, J Bone Miner Res 7(Suppl 2):S419-S424, 1992.

Arokoski JP, Hyttinen MM, Lapvetelainen T, et al: Decreased birefringence of the superficial zone collagen network in the canine knee (stifle) articular cartilage after long distance running training, detected by quantitative polarised light microscopy, Ann Rheum Dis 55:253-264, 1996.

Lammi M, Hakkinen TP, Parkkinen JJ, et al: Adaptation of canine femoral head articular cartilage to long distance running exercise in young beagles, Ann Rheum Dis 52:369- 377, 1993.

Vasan N: Effects of physical stress on the synthesis and deg- radation of cartilage matrix, Conn Tiss Res 12:49-58, 1983.

Chang Qi, Huang Changlin: Effects of moving training on histology and biomarkers levels of articular cartilage, J Surg Res 135:352-363, 2006.

Newton PM, Mow VC, Gardner TR, et al: The effect of lifelong exercise on canine articular cartilage, Am J Sports Med 25:282-287, 1997.