Juvenile Arthritis and Bone Health: Risks, Prevention, and Treatment

Kids build up to 90% of their adult bone by age 18. That’s your child’s “bone bank,” and active inflammation, pain, and long steroid courses can drain it fast. If you’re wondering how arthritis in childhood links to weak bones, fractures, and growth issues-and what you can do about it today-you’re in the right place. I’m a mum in Dunedin with a child who has arthritis, and I’ve been through the scans, the supplements, and the school letters. Here’s the practical, evidence-backed version I wish someone handed me early on.

• TL;DR
• Inflammation, inactivity, and steroids lower bone density in kids with juvenile arthritis; biologics that control disease can protect bones.
• Ask for a DXA scan if there are fractures, long-term steroids, poor growth, or high disease activity; use Z-scores (not T-scores) and adjust for height.
• Daily plan: 1,000-1,300 mg calcium (by age), 600 IU vitamin D (more if deficient), 30-60 minutes weight-bearing most days, sleep, and treat the disease to target.
• Red flags: low-trauma fractures, back pain, falling percentiles for height, or prednisone longer than 3 months.
• Severe low density or fragility fractures may need pediatric endocrine input and bisphosphonates.

How juvenile arthritis affects growing bones

Bone is alive. It’s constantly being broken down and rebuilt by cells (osteoclasts and osteoblasts). In active arthritis, inflammatory signals like TNF, IL‑1, and IL‑6 tip that balance toward breakdown. That’s the core link: higher inflammation, lower bone formation.

Several things pile on at once:

• Disease activity: Cytokines increase RANKL signaling, which drives osteoclasts. Children with higher joint counts and inflammatory markers tend to show lower bone mineral density (BMD) on scans.
• Less movement: Pain and stiffness reduce weight-bearing activity, and bone responds by getting weaker. Bone is “use it or lose it.”
• Steroids: Prednisone helps during flares, but chronic use reduces bone formation, increases resorption, and can slow growth. Risk rises with doses around 0.2 mg/kg/day for more than 3 months.
• Growth and puberty: Inflammation can delay puberty and blunt the growth spurt-exactly when most bone is added.
• Nutrition: Appetite dips during flares and meds can trigger nausea. Low calcium, low vitamin D, and low protein make it harder to build bone.

What does the research say? Meta-analyses show children with arthritis have lower BMD at the lumbar spine and total body, often by about half to one standard deviation on average. Clinically, that means higher odds of fractures if nothing changes. The good news: when inflammation is tightly controlled (treat-to-target), bone accrual improves.

Guidelines worth knowing: Pediatric bone density is assessed differently from adults. The International Society for Clinical Densitometry (ISCD) recommends using Z-scores (age- and sex-matched), not T-scores, and adjusting for height in smaller kids. The ISCD also defines pediatric osteoporosis as low BMD (Z ≤ −2.0) plus a clinically significant fracture history (for example, two or more long-bone fractures by age 10, or three or more up to age 19), or one or more vertebral compression fractures without major trauma.

My reality check as a parent: my daughter Tilda had a classic winter flare and a wrist fracture from a minor fall at seven. That was my cue to push for a DXA, a vitamin D test, and a rethink of her activity plan. We found low vitamin D, bumped her intake, tightened disease control, and kept water-based fitness while adding short, gentle impact sessions on good days. It made a measurable difference.

How to spot bone risk early (and what to test)

Red flags you shouldn’t ignore:

• Low-trauma fractures (for example, a wrist fracture from a short fall at the playground)
• Back pain or height loss suggesting possible vertebral fractures
• Prednisone for longer than 3 months or multiple steroid bursts per year
• High disease activity over months
• Faltering growth or delayed puberty
• Restricted diet, poor appetite, or weight loss

What to ask your care team to check:

• Blood tests: 25‑hydroxy vitamin D (25[OH]D), calcium, phosphate, alkaline phosphatase, and parathyroid hormone if calcium or vitamin D are off. Consider celiac screening if growth is poor or iron is low.
• DXA scan: Lumbar spine and total body less head (TBLH). Make sure the report gives Z-scores and mentions height adjustment in smaller kids.
• Vertebral assessment: A lateral spine image (DXA-based VFA or X‑ray) if there’s persistent back pain or height loss.

When to scan:

• Now if your child has had a low-trauma fracture, vertebral pain, prolonged steroids, or significant growth delay.
• Within 6-12 months of starting a steroid-sparing plan if bone risk is high, then repeat every 1-2 years depending on results and disease control.

How to read the report (without needing a PhD):

• Use Z-score, not T-score. Z = 0 is average for age; Z = −2.0 means 2 SD below average.
• Ask whether height-adjusted Z-scores were used. Children who are shorter than peers can look falsely low on bone density if height isn’t considered.
• One low Z-score alone isn’t the whole story-pair it with clinical history (fractures, growth, meds).

Important pitfall: Adult fracture calculators like FRAX don’t apply to kids. Stick to pediatric criteria.

Your daily plan to build strong bones (simple, doable, repeatable)

Nutrition targets (based on common pediatric recommendations):

• Calcium: 1-3 years: 700 mg/day; 4-8 years: 1,000 mg/day; 9-18 years: 1,300 mg/day.
• Vitamin D: 600 IU/day is a typical maintenance target; if 25(OH)D is low, your clinician may prescribe a short course of higher dosing, then recheck.
• Protein: Aim for a serving at each meal (roughly a palm-sized portion of meat/beans/tofu for older kids; smaller for younger).

Food ideas that actually fit into a school day:

• Breakfast: Greek yoghurt with berries and oats; or fortified soy milk smoothie with spinach and peanut butter; or eggs on wholegrain toast.
• Lunchbox: Cheese or hummus sandwich, carrot sticks, a yoghurt pot, and a piece of fruit.
• Dinner: Stir-fried tofu with broccoli and sesame; salmon with kumara; lentil dahl with spinach and flatbread.
• Snacks: Milk or fortified plant milk, edamame, almonds (if safe), or a cheese stick.

Dairy-free or vegan? Choose fortified milks (aim for 300 mg calcium per cup), calcium-set tofu, leafy greens, tahini, almonds, and consider a calcium and vitamin D supplement. If food allergies limit options, a dietitian can build an easy plan around your child’s preferences.

Vitamin D and sun: In New Zealand, UV is intense in spring/summer. Short, regular bursts of sun on arms and legs are usually enough for maintenance in fair skin, but sunscreen still matters to prevent burns. Winter levels dip, so testing and supplements are often needed for kids with arthritis. Many specialists aim for 25(OH)D at or above 50 nmol/L; some prefer closer to 75 nmol/L in high-risk kids. Don’t megadose without labs.

Movement plan by disease state:

• On calm days: 30-60 minutes of weight-bearing most days. Think brisk walking, playground climbing, hopscotch, light jogging, dancing, basketball hoop time, or gentle skipping rope. Add 2-3 short sessions of muscle strengthening (bodyweight, resistance bands) per week.
• During flares: Keep joint range with physio-led stretches, isometric holds (gentle muscle contract/relax), short water sessions (pool walking), and low-impact stationaries like cycling. Resume impact in small doses as pain settles.
• Teens: Add technique-coached strength training 2-3 days/week. Start light, focus on form, and progress slowly.

Simple weekly template (edit to your child):

• Mon: 20-30 min brisk walk + 10 min band exercises
• Tue: Swim or cycling 20 min + stretch
• Wed: Playground (climb, steps, light hops) 20-30 min
• Thu: Rest or yoga/mobility 15 min
• Fri: Dance or PE 30-45 min
• Sat: Family bush walk 45-60 min (pick flat tracks on flare weeks)
• Sun: Short band session + easy bike ride

Sleep and soft drinks: Chronic short sleep and lots of sugary soft drinks aren’t bone-friendly. Aim for age-appropriate sleep and keep fizzy drinks as occasional treats.

School note: A short letter from your clinician or physio can help teachers adjust PE on flare days without sidelining your child from weight-bearing activity entirely.

Medicines: what helps bones, what hurts, and how to balance it

Steroids (prednisone): Great for stopping a flare; rough on bones in the long run. Risk rises with daily dosing over months. Ask your rheumatology team about a steroid-sparing plan-faster ramp-up of disease-modifying drugs, taper schedules, and intra-articular injections when appropriate.

Intra-articular steroids: A few targeted joint injections have far less systemic bone impact than long courses of daily oral steroids.

NSAIDs: Neutral for bone density. They help pain and function, which can support activity and indirectly help bone.

Methotrexate: No strong direct harm to bone at standard pediatric doses. The main issue is nausea or fatigue reducing appetite and activity-plan meals and anti-nausea strategies on dose day.

Biologics (e.g., TNF or IL‑6 inhibitors): By cutting inflammation, these often improve bone accrual over time. Studies show BMD can stabilise or climb when disease activity is controlled to target.

Other meds to have on your radar:

• Proton pump inhibitors (PPIs): Long-term use may reduce calcium absorption; review ongoing need.
• Certain anti-epileptic drugs: Can lower vitamin D. Ask for vitamin D monitoring.
• Depot medroxyprogesterone (DMPA) in teens: Can slow bone accrual; discuss alternatives if bone density is low.

Evidence touchpoints: The American College of Rheumatology (2021) supports treat-to-target care in juvenile idiopathic arthritis to reduce damage and medication toxicity. Children’s bone guidance from ISCD (pediatric positions) explains how to measure and interpret BMD properly. Pediatric glucocorticoid-induced osteoporosis guidance (Endocrine and rheumatology groups) emphasises nutrition, activity, disease control, and cautious use of bisphosphonates for severe cases.

Real-world tip from clinic days: A small change that sticks beats a perfect plan that collapses. If your child only tolerates 10 minutes of walking after school on flare weeks, bank it. Consistency wins.

When bone density is low: action steps, checklists, and what to expect

If your child’s Z-score is low or they’ve had fragility fractures, you need a tight plan that covers disease control, nutrition, activity, and-sometimes-bone-targeted therapy.

Immediate steps (first 1-3 months):

• Set a disease activity target with your rheumatologist (remission or low disease activity). Escalate treatment early if needed.
• Check 25(OH)D and correct deficiency. Recheck in 8-12 weeks after a loading plan.
• Hit calcium targets with food first; add a supplement if intake is short by more than 300-500 mg/day.
• Start a physio-designed program mixing low-impact movement on flare days and short-impact bouts on good days.
• Log pain, activity, flares, and any falls or injuries. Small patterns guide smarter adjustments.

Follow-up steps (3-12 months):

• Repeat vitamin D if it was low; tweak maintenance dose.
• DXA at 12-24 months depending on risk and the first result. Consider earlier imaging if there’s a new fracture or persistent back pain.
• If Z ≤ −2.0 and fractures occur, ask for a pediatric bone specialist (endocrinology or a bone health clinic) consult.

About bisphosphonates: In children, these are reserved for clear cases-vertebral compression fractures or repeated long bone fractures with very low Z-scores. They stabilise or increase BMD and reduce pain in vertebral fractures. They’re given by infusion (like pamidronate or zoledronic acid) under specialist care, with monitoring of calcium and vitamin D. They’re not first-line for “slightly low” numbers without fractures.

What won’t help: Random high-dose vitamin D “just in case,” avoiding all impact forever, or waiting for growth to “catch up” while inflammation smoulders. Controlling disease and small bits of regular impact are the levers that move the needle.

Quick checklists

Home checklist (weekly):

• Food: Did we roughly hit calcium targets? If not, add one fortified milk or yoghurt a day.
• Vitamin D: Are we on the maintenance plan? Any recheck due?
• Movement: 4-6 days with at least a short weight-bearing session? Swap swimming-only weeks for a couple of walk/dance days.
• Sleep: Are we within age-appropriate hours? Adjust bedtime if not.
• Flare plan: Do we have isometric moves and stretches ready for tough days?

Clinic checklist (bring this to appointments):

• Any new falls or fractures? Back pain or height changes?
• Prednisone use since the last visit (dose and days)?
• Activity log highlights: what works, what hurts?
• Vitamin D result and date; calcium intake estimate
• Do we need: height-adjusted DXA, spine imaging, physio update, or a steroid-sparing tweak?

Mini‑FAQ

Does swimming count for bone? It’s excellent for joints, heart, and mental health, but it’s not weight-bearing. Keep it, and add short, regular on-land sessions.

Is trampolining safe? Short, supervised sessions on a netted trampoline can help impact loading, but avoid flips and crowded bouncing. If your child has a recent fracture or severe flare, wait and ask your physio first.

What vitamin D level should we aim for? Many clinicians aim for at least 50 nmol/L (20 ng/mL). Some aim for 75 nmol/L (30 ng/mL) in high-risk kids. Test, treat, and recheck rather than guessing.

Can a teen on Depo‑Provera keep using it? Possibly, but discuss bone risks if density is low. Alternatives may be better until bone accrual improves.

Does methotrexate damage bones? Not directly at usual doses. Indirect effects (nausea, less activity) can matter-manage those and keep moving.

How fast can bone improve? You can see vitamin D correct in weeks; BMD changes over months to a year. Controlled inflammation and steady habits compound over time.

Next steps and troubleshooting

If your child is on daily steroids longer than 3 months: Ask for a steroid-sparing plan and a DXA referral. Add or escalate a DMARD/biologic per your rheumatologist’s guidance.

If there’s a low-trauma fracture: Request labs (25[OH]D, calcium, phosphate), consider vertebral imaging if there’s back pain, and ask for a DXA with height-adjusted Z-scores.

If vitamin D stays low despite supplements: Check adherence, dosing form (drops vs tablets), absorption issues (consider celiac screening), and timing with meals containing fat.

If activity triggers pain: Break sessions into 5-10 minute chunks, switch surfaces (grass beats concrete), use cushioned shoes, and schedule movement when meds are “on board.”

If scans and labs look fine but you’re worried: Keep the plan anyway. Good sleep, steady nutrition, and regular movement support joints, mood, and bone-this is a long game.

Sources I trust and echo here: American College of Rheumatology (2021) guidelines for juvenile idiopathic arthritis (treat-to-target), International Society for Clinical Densitometry pediatric positions on DXA and fracture definitions, pediatric glucocorticoid-induced osteoporosis guidance from endocrine and rheumatology groups, and recent meta-analyses showing reduced BMD in children with arthritis that improves when inflammation is controlled. Use these as talking points with your team; they’re the backbone of modern care.