Rickets in puppies: symptoms, causes and bone treatment

Overview

Rickets affects young, growing animals because it involves open growth plates. A growth plate is a cartilage region through which a bone lengthens. In rickets, cartilage accumulates but does not develop into normally mineralised bone. Bones may therefore soften, bend and fracture.

Nutritional rickets is rare in dogs. However, disorders of skeletal mineral metabolism are not all the same disease. Osteomalacia involves impaired mineralisation during bone tissue renewal, whereas rickets is characterised by changes in growth cartilage. The precise diagnosis determines which aspects of feeding and treatment need correction.

Causes

Calcium, phosphorus and vitamin D must work together

Rickets can result from insufficient phosphorus or calcium, an incorrect balance between them, or inadequate active vitamin D. Dietary fats and bile acids help vitamin D absorption in the small intestine. Vitamin D promotes intestinal calcium and phosphate absorption. Active vitamin D also reduces renal mineral losses by promoting calcium and phosphate reabsorption. Dietary vitamin D is first converted in the liver to a form reflecting stores, then in the kidneys to active calcitriol.

A meat-only diet may be mineral-imbalanced. Many home-made diets lack adequate mineral balance even when the meal looks varied. In growing puppies, high dietary calcium can also reduce phosphorus absorption, making normal skeletal mineral balance harder to maintain. Calcium cannot be added without limit: a threefold concentration has caused rickets-like changes in growing Great Danes.

When blood calcium falls, parathyroid hormone secretion increases and stimulates vitamin D activation. Low dietary calcium with high phosphorus can also cause nutritional secondary hyperparathyroidism. Associated fibrous osteodystrophy involves bone loss and replacement with fibrous tissue. Renal phosphorus wasting can also cause phosphorus-deficiency rickets.

An inherited form can prevent vitamin processing

A CYP27B1 gene defect can prevent conversion of vitamin D to its active form despite adequate dietary intake. In another inherited form, the vitamin D receptor does not respond normally to the active vitamin.

Risk factors

Risk primarily relates to growth and whether the diet meets a growing puppy's needs. Large breeds are sensitive to diet-related growth disorders when energy or minerals are imbalanced. Between around 6 weeks and 6 months, passive calcium absorption directly depends on dietary calcium quantity. Excess intake can also increase osteochondrosis, a developmental joint cartilage disorder, and slow normal growth. Food designed solely for adults does not automatically meet a growing puppy's needs, because foods serve different life stages.

Inherited defective vitamin D activation has been identified in related Pugs. Two affected Pugs underwent imaging at 5 and 6 months old. This demonstrates a possible inherited cause but does not mean every Pug's bone pain is rickets. Dietary assessment is also needed when close relatives have similar growth and mobility problems.

Typical symptoms

Lameness may be the first visible functional problem in a growing dog with rickets. It can range from mild limping to inability to walk. Signs at home include:

• Lameness or a stiffer gait than usual.
• Difficulty rising from lying down.
• Reluctance to move and play normally.
• Bowed limbs or abnormal limb positioning.
• Pain when a bone or growth plate region is felt.
• Swelling around the ends of bones.
• Remaining smaller than expected or slowing growth.

One Pug with inherited disease initially developed normally according to the owner, with deformities noticed only after 13 weeks. Signs may progress until a previously mobile puppy avoids standing. A fracture can cause sudden deterioration. However, a visibly bowed limb does not establish the cause: growth plates need imaging.

Complications and consequences

Weakened bone can fracture without the substantial trauma needed to break healthy bone. Vertebral fractures from nutritional bone disease can compress the spinal cord and prevent hindlimb walking. Changes can affect vertebral and rib growth plates as well as limbs. Paired bones growing at different rates can cause permanent limb deformity.

The outlook is good if fractures or permanent growth plate damage have not developed. Advanced inherited disease can be life-threatening. In one treated Pug with inherited disease, bone pain had resolved and limb alignment straightened at 6 weeks, although growth remained slow. This is one dog's recovery observation rather than a correction timescale for every puppy.

Diagnosis at the vet

Diet and X-rays form the basis of investigation

Your vet reviews the entire diet, including supplements, treats and any home-made recipe. Food can be assessed with nutrient calculations or laboratory testing when needed. A Giant Schnauzer with nutritional bone disease had a measured dietary calcium-to-phosphorus ratio of 1:4. Vitamin D in this puppy's diet was below the laboratory detection limit despite added supplements. An ingredient list alone does not establish the full mineral balance.

Long bone and joint X-rays are the main way to demonstrate typical rickets changes in a living animal. Growth plates appear wider and more irregular than usual. Bone radiographic density may be reduced. A dog with spinal signs may need more detailed imaging to assess cord compression.

Blood tests assess minerals and different vitamin D forms

Calcium, phosphorus, vitamin D and, when needed, parathyroid hormone, or PTH, are tested. Bone-related alkaline phosphatase, or ALP, activity is often raised. The combination of results depends on the metabolic step affected.

The usual storage form has a half-life of around 10 days to 3 weeks, but active calcitriol only 3–6 hours. The storage form, calcidiol, travels from liver to kidneys bound to a specific carrier protein. Routine calcidiol measurement primarily reflects vitamin D intake and storage. In inherited activation failure, this result may be adequate despite very low active vitamin. Total calcium in two affected Pugs was 1.6 millimoles per litre, compared with 2.8 in a healthy sibling of the same age. Active vitamin D was respectively 9 and 8 picomoles per litre in the affected puppies, compared with 566 in the healthy sibling.

These are comparisons between individual dogs rather than diagnostic thresholds for every laboratory. Suspected renal phosphorus wasting also requires urine phosphorus assessment. Genetic testing or a bone sample may provide more information in unusual or suspected inherited cases.

Treatment

Diet is corrected according to the confirmed deficiency

The first step is identifying and correcting missing nutrients and their imbalance. A balanced complete puppy food or diet formulated by a veterinary nutrition specialist is selected. Energy intake and growth rate are also considered in large-breed puppies.

Your vet prescribes medication and any vitamin or mineral treatment. During nutritional bone disease treatment, weight and body fat condition are reassessed to avoid weight gain during reduced exercise. Vertebral fractures in the Giant Schnauzer with nutritional bone disease were managed with 6 weeks of rest. Exercise was increased gradually to strengthen muscles as condition improved.

Inherited activation failure needs targeted treatment

Defective vitamin D activation may require the active vitamin form because ordinary intake alone cannot correct the conversion defect. In the treated Pug, blood calcium corrected within 2 weeks before full willingness to exercise returned. Calcium is also monitored to detect excessive increases. Too much vitamin D can raise calcium and cause signs such as increased drinking, vomiting and poor appetite.

Recovery is assessed through movement, growth, blood tests and repeat X-rays when needed. Calcium and active vitamin D in the treated Pug remained appropriate at 22 months old. Established bone deformity can persist even when metabolism is corrected.

Prevention

Nutritional rickets is prevented by ensuring balanced mineral and vitamin intake during growth. On labels using these feed categories, 'complete feed' means food that meets daily nutritional needs on its own. 'Complementary feed' supplements other food and means something different. Also check the stated life stage, because puppies and adults have foods intended for them.

Keep unbalanced treats and home-made extras to no more than 10% of daily energy so they do not displace the growing dog's main food. Adding calcium yourself to an already balanced ration can disrupt skeletal growth. Sun exposure does not replace dietary vitamin D, because dogs do not produce it in their skin like humans. An inherited activation defect cannot be prevented simply by changing food.

Important for dog owners

Bring packaging or clear contents information for every food and supplement. Write down the home-made recipe with quantities and include treats. Explain when movement changed and whether littermates show similar signs. Monitor weight, standing posture and willingness to rise, but do not bend a painful limb to examine it yourself.

Follow prescribed exercise restrictions and prevent rough play during fracture recovery. Do not add vitamin D or calcium yourself to prescribed treatment. Agree follow-up appointments and practical instructions for carrying and walks. Excessive drinking and urination developing during treatment may relate to rising blood calcium. Report these signs to your vet.

Frequently asked questions

Can a puppy eating complete food develop rickets?

Nutritionally balanced food prevents deficiencies but does not remove every inherited cause. A gene defect disrupting vitamin activation, for example, can cause rickets despite adequate intake. Lameness or poor growth therefore still needs investigation regardless of the food label.

Does sunlight help rickets in dogs?

Dogs need vitamin D from food because they cannot produce it in their skin using sunlight. More outdoor time does not correct dietary vitamin and mineral balance. Treatment identifies a deficiency or metabolic defect and corrects it according to your vet's plan.

Can I give a limping puppy extra calcium?

Adding calcium yourself is not a safe way to investigate lameness. Excess calcium has caused rickets-like growth disorders in Great Dane puppies. Phosphorus or active vitamin D problems may also underlie rickets. Diet and any supplements are therefore assessed alongside investigation results.

Will bowed legs straighten completely?

The outlook is good if fractures or irreversible growth plate damage have not developed. Advanced skeletal changes can remain permanent. Recovery assessment therefore follows pain, daily movement, growth and skeletal structure.

Is rickets the same as osteodystrophy?

Rickets involves inadequate mineralisation of growth cartilage and impaired new bone formation. In fibrous osteodystrophy, bone breaks down and is replaced by fibrous tissue. Nutritional deficiency can cause both changes in one dog, involving several mechanisms of skeletal weakening. Dietary history, blood tests and skeletal imaging are therefore needed to identify the precise changes.