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from the American Academy of Orthopaedic Surgeons

Diseases & Conditions



Staying Healthy

Lyme Disease

Lyme disease is an infection caused by a bacteria normally found in deer and transmitted to humans by deer ticks. The deer tick is found in grassy areas, so people who work, play and hike in these areas are at particular risk. It is not known how long the tick needs to be in contact with the skin in order to transmit the disease.

Lyme disease was first described in 1975. It has been identified in almost all the states. Most cases happen in people who live in, or have recently traveled to, the Northeastern and upper Midwest regions of the country. People of any age can get it. Late spring and summer are peak seasons.


Tell your doctor if you travel to areas of high risk for Lyme disease, especially during summer months.

Taking precautions is very important to avoid getting this potentially dangerous condition.

  • While hiking, stay on hiking trails and avoid deep grassy areas. Wear pants, long sleeve shirts, and high socks.
  • Check for ticks on household pets and anyone who may have come in contact with high-risk areas.
  • If a tick bite is suspected, contact your family physician immediately.


Symptoms are complex and sometimes confusing.

The infection begins at the site of the tick bite. Most people do not remember a tick bite or finding a tick on their body.

There may be a red spot that looks like a target shape.

A rash develops at the site of the bite and spreads to other parts of the body (Erythema migrans).

In initial stages, Lyme disease causes flu-like symptoms of fever, malaise, rash, neck stiffness, and joint pain. These symptoms may take days or weeks to show up. Other symptoms include the chills.

Joints may become tender with minimal swelling and no redness. The knee is the joint most often affected.

In later stages, the disease affects the heart and nervous system and causes Lyme arthritis.


See your doctor to diagnose Lyme disease.

He or she may use imaging studies to help make the diagnosis.

  • In acute stages, X-rays of affected joints may show soft-tissue swelling.
  • In the chronic stage, signs of swelling, joint fluid, and arthritis may be seen.

Using only an analysis of the blood to diagnose Lyme disease can be difficult. The signs of inflammation, such as the white blood count, sedimentation rate, and C-reactive protein will be higher, but this is true of other diseases in addition to Lyme disease.

Specific tests, such as serologies, may take up to four weeks to six weeks to become higher than normal (elevated). An elevated serum titer indicates that the body is responding to an exposure to the bacteria. However, the bacterial infection may have been cleared and so an elevated serum titer does not necessarily reflect an active infection.

If joint swelling is present, a culture of the fluid may indicate the presence of an active infection, but is only positive about 60 percent to 70 percent of the time. A more sensitive test called PCR is being developed to detect the presence of the bacteria.

Lyme disease is usually suspected in an individual who has been exposed, has a tick bite, and has joint pain. In cases where it is not clear if the patient has been exposed, the doctor will need to rule out other potential causes for the symptoms. These can include soft-tissue infections, septic arthritis, and rheumatologic diseases, such as juvenile arthritis.


Most cases of Lyme disease respond to a one-month course of antibiotics. The appropriate antibiotic depends on the patient's age, allergies, and special medical conditions (such as pregnancy).

The prognosis is excellent if the infection is recognized early. Even with treatment, a small number of individuals can go on to develop chronic arthritis.

The prophylactic treatment for an individual presenting after finding a tick on their body is controversial. Talk with your doctor. A vaccine has been developed, but it is currently not recommended because of potential side effects.

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Reviewed by members of
POSNA (Pediatric Orthopaedic Society of North America)

The Pediatric Orthopaedic Society of North America (POSNA) is a group of board eligible/board certified orthopaedic surgeons who have specialized training in the care of children's musculoskeletal health. 

Last Reviewed

July 2007

AAOS does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific orthopaedic advice or assistance should consult his or her orthopaedic surgeon, or locate one in your area through the AAOS Find an Orthopaedist program on this website.