Growing Pains or Lyme Disease? How to Tell the Difference

Growing pains usually affect both legs at night.
Joint swelling, daytime pain, or limping does not fit the typical pattern.
Lyme disease is one possible explanation that deserves consideration.

A nine-year-old complains of knee pain at bedtime. A twelve-year-old wakes up crying with leg aches. A teenager begins limping after soccer practice.

When children report leg or joint pain, “growing pains” may become the default explanation. Often, that diagnosis is reassuring and appropriate. But the label should not be applied automatically when a child has persistent, one-sided, or function-limiting pain.

Lyme arthritis often causes visible swelling of a large joint—particularly the knee—and may be accompanied by stiffness, limited movement, or limping. These findings are not expected with typical growing pains.

For a broader discussion of why Lyme disease may be overlooked in children, see Pediatric Lyme Disease: Why Children Are Often Misdiagnosed.

Why Growing Pains and Lyme Disease Get Confused

Both conditions may involve leg discomfort during childhood. Symptoms may also be more noticeable after an active day. However, the location, timing, physical findings, and effect on daily activity are usually different.

Growing pains describe a recognizable pattern of recurring limb pain in an otherwise healthy child with a normal physical examination. Lyme disease may cause muscle and joint pain, but Lyme arthritis produces objective inflammation, most often involving one or a few large joints.

Relying too quickly on the growing pains label may delay evaluation when the child’s symptoms do not fit the usual pattern.

What Typical Growing Pains Look Like

Growing pains are generally non-articular pains, meaning the discomfort is felt in the muscles rather than inside a joint.

The typical pattern includes:

• Pain in both legs
• Aching in the thighs, calves, shins, or behind the knees
• Symptoms occurring in the late afternoon, evening, or at night
• Pain that resolves by morning
• Pain-free days between episodes
• Normal walking, running, and playing during the day
• No joint swelling, warmth, redness, or restricted movement

Although the name suggests otherwise, growing pains have not been shown to result directly from rapid growth or a growth spurt.

Growing Pains vs. Lyme Disease: Key Differences

Important: These distinctions are guides rather than diagnostic rules. Lyme disease does not present identically in every child, and several other conditions can also cause persistent pain, swelling, or limping.

When the Pain Needs a Closer Look

Certain findings do not fit the usual pattern of growing pains and warrant further evaluation:

• Visible swelling of the knee, ankle, or another joint
• Pain affecting only one leg, particularly when it repeatedly occurs in the same location
• Persistent or worsening pain lasting days or weeks
• Morning stiffness or pain that remains after waking
• Daytime symptoms that interfere with school, sports, or play
• Limping or refusal to bear weight
• Warmth, redness, or limited movement of a joint
• Focal tenderness over a bone
• Weakness, numbness, or tingling
• Fever, rash, fatigue, headache, pallor, bruising, poor appetite, or weight loss
• Possible tick exposure or outdoor activity in an endemic area

These warning signs do not automatically mean that a child has Lyme disease. They indicate that the pain should not be dismissed as a normal part of growing.

How Lyme Arthritis Presents in Children

Lyme arthritis most often affects large joints, particularly the knee.

A child may develop substantial swelling with stiffness, warmth, or reduced range of motion. Symptoms may persist or occur in episodes. One or more joints may be affected over time.

Children may limp, avoid stairs, stop participating in sports, or become less active. A child with Lyme arthritis does not always appear acutely ill, and the amount of swelling may be more striking than the reported pain.

Lyme arthritis frequently appears months after the initial infection. By that time, an early rash or flu-like illness may have resolved or may never have been recognized. Many children and parents do not recall a tick bite.

Lyme disease does not always begin with obvious joint swelling. Some children initially report intermittent muscle, bone, or joint pain accompanied by fatigue, headaches, disrupted sleep, or declining stamina. The importance lies in the complete clinical pattern rather than any single symptom.

Not Every Atypical Pain Is Lyme Disease

Lyme disease is only one possible explanation for childhood limb pain. Depending on the history and physical examination, clinicians may also consider:

• An injury or overuse condition
• Juvenile idiopathic arthritis
• Septic arthritis or a bone infection
• Joint hypermobility or a mechanical problem
• Vitamin D deficiency or another nutritional problem
• Neurologic or muscular disorders
• Other inflammatory or autoimmune illnesses
• Blood disorders or, less commonly, malignancy

The goal is not to test every child with nighttime leg pain for every possible disease. It is to recognize when the history or examination no longer supports a benign growing pains pattern.

The Diagnostic Challenge

Growing pains are diagnosed clinically. When the history is characteristic and the physical examination is normal, laboratory testing and imaging are generally unnecessary.

Children with joint swelling, persistent daytime pain, limping, fever, focal tenderness, weakness, or other atypical findings require a more individualized evaluation.

When Lyme arthritis is suspected, the clinician should consider the joint findings, geographic and seasonal exposure, outdoor activities, prior rashes, and other symptoms. Children with Lyme arthritis generally have positive Lyme serology because arthritis usually develops after the immune system has had time to produce detectable antibodies.

Test results must still be interpreted alongside the child’s clinical presentation. For more information, see Lyme Disease Test Accuracy: Timing, Limitations, and Clinical Diagnosis.

A child with persistent knee swelling after summer camp deserves evaluation for Lyme disease even if the discomfort was initially described as growing pains.

Why This Distinction Matters

Typical growing pains are benign and generally improve with reassurance, massage, warmth, stretching, or age-appropriate pain relief when recommended by a healthcare professional.

Lyme arthritis requires antibiotic treatment. When the diagnosis is delayed, a child may experience prolonged swelling, restricted activity, missed school, and unnecessary pain.

Recognizing that a child’s symptoms no longer fit growing pains allows the clinician to investigate Lyme disease and other possible causes sooner.

Frequently Asked Questions

How can I tell if my child has growing pains or Lyme disease?

Typical growing pains affect the muscles of both legs, occur mainly in the evening or at night, resolve by morning, and do not cause swelling or limping. Lyme arthritis commonly involves swelling of a large joint, particularly a knee, and may cause daytime stiffness, limited movement, or limping.

Can Lyme disease cause leg pain at night?

Yes. Lyme disease may cause pain at any time. However, Lyme arthritis commonly produces joint swelling or symptoms that remain during the day. Nighttime pain accompanied by daytime stiffness, swelling, or limping deserves further evaluation.

Can growing pains occur in only one leg?

Typical growing pains generally affect both legs. Pain that repeatedly affects only one leg—especially with swelling, focal tenderness, morning symptoms, or limping—should be medically evaluated.

What does Lyme arthritis look like in children?

Lyme arthritis often causes visible swelling of a large joint, particularly the knee. The joint may also feel warm or stiff and have limited movement. Some children limp or reduce their usual activities, while others remain surprisingly active despite substantial swelling.

Do growing pains cause knee swelling?

No. Visible knee swelling is not a feature of typical growing pains. A swollen joint requires medical evaluation because Lyme arthritis and several other conditions can produce this finding.

Clinical Takeaway

Growing pains typically cause recurring muscle discomfort in both legs during the evening or at night. The child is well during the day, the pain resolves by morning, and there is no swelling, limping, or loss of joint movement.

Joint swelling, persistent one-sided pain, morning stiffness, limping, focal tenderness, or declining activity does not fit the classic pattern. Lyme disease is one possible explanation, but the child should be evaluated for other causes as well.

Related Articles

• Pediatric Lyme Disease: Why Children Are Often Misdiagnosed
• Lyme Arthritis and Knee Swelling in Children
• Lyme Disease Test Accuracy
• MRI Can Help Identify Lyme Arthritis in Children

References

1. Gerber MA, Shapiro ED, Burke GS, et al. Lyme disease in children in southeastern Connecticut. N Engl J Med. 1996;335(17):1270–1274.
2. Uziel Y, Hashkes PJ. Growing pains in children. Pediatr Rheumatol Online J. 2007;5:5.
3. Lehman PJ, Carl RL. Growing pains. Sports Health. 2017;9(2):132–138.
4. Pavone V, Vescio A, Valenti F, et al. Growing pains: What do we know about etiology? A systematic review. World J Orthop. 2019;10(4):192–205.

This article is intended for educational purposes and is not a substitute for individualized medical advice, diagnosis, or treatment.

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention