Limp

A three-year-old child presents with a chief complaint of not bearing weight on his right leg for the past two days. There are no known injuries, however he is a very active child. He has also had a fever since last night, with a maximum temperature at home of 102°F. The family denies cough, congestion, vomiting, diarrhea, or sore throat. Prior to this, the patient had been completely healthy. The caregivers have been alternating between ibuprofen and acetaminophen around the clock for the fevers as well as pain, with no relief.

He is ill-appearing on exam, with vital signs including a temperature of 39.0°C, heart rate 140, respiratory rate 18, blood pressure 100/65, and pulse oximetry 99% on room air. He is lying in bed with his right leg flexed and externally rotated at the hip. He does not let you palpate it or move it and refuses to try to stand on it. Otherwise, his head and neck exam is normal, his lungs are clear, his abdomen is soft and non-tender, and you do not see any rashes. The remainder of his extremity exam is unremarkable.

As mentioned, the differential for this patient presentation is broad, but in general can be broken down into traumatic and non-traumatic causes.

• Traumatic: Fractures, toddler's fractures, stress fractures/overuse injuries, dislocations (patellar, hip, ankle), muscle strains/sprains, ligament tears (ACL, PCL, meniscus), foreign bodies.
• Non-Traumatic: Septic joints, transient synovitis, reactive arthritis, rheumatologic conditions (JIA, ankylosing spondylitis), osteomyelitis, developmental dysplasias, slipped capital femoral epiphysis (SCFE), avascular necrosis, legg-calve-perthes (LCP), neoplasms (osteosarcoma, Ewing sarcoma, leukemia).

In attempting to narrow down the differential, the following should be considered.

History

Age of the Child

Is the child even limping, or is their gait age-appropriate? Teenagers, especially those who are athletic, are more predisposed to stress fractures or overuse injuries. This is also the age group where bony neoplasms (osteosarcoma, Ewing sarcoma) are most likely to occur. SCFEs are commonly seen in the preteen group, especially if overweight.

History of Trauma

This may be difficult to elicit, but did they fall? If they did, was the injury age-appropriate? For example, non-accidental trauma needs to be considered for any non-ambulatory child with a lower extremity fracture. If there is trauma, what is the mechanism? Landing hard on a straight leg can lead to a tibial or femoral buckle fracture. Landing and then twisting, or having the extremity get caught on a person or object (i.e. the leg gets caught on a slide while sitting on their parents lap and is bent backwards) can be seen with spiral toddlers fractures.

Duration of Pain

How long have the symptoms been present? Acute pain often suggests an injury, while chronic pain is often a sign of an inflammatory, infectious, or neoplastic condition.

History of Recent Illnesses

The presence of a fever suggests infectious or inflammatory causes. It is important to review any recent illnesses from the past few weeks to a month. Transient synovitis will be seen as a reaction to a recent viral, usually upper respiratory, infection.

Exacerbating Factors

Is it worse with weight-bearing? Is the time of day a factor? Pain secondary to neoplastic processes is typically worse at night. Pain that gets worse after the onset of activity may suggest a stress fracture or overuse injury, while pain that improves with activity may suggest an underlying rheumatologic etiology. If the pain only occurs with walking but the child is able to crawl, it may be indicative of a foot foreign body.

Associated Symptoms

Fevers, rashes, or pain in multiple joints can be infectious or rheumatologic. Recent weight loss, fatigue, or night sweats can be associated with an oncologic process. Associated abdominal complaints can be associated with acute appendicitis and psoas muscle abscesses.

Other Underlying Medical Conditions

If the child has sickle cell disease, pain may represent an acute pain crisis or avascular necrosis of the hip. Obesity puts the child at risk for SCFE. If the child has cerebral palsy or muscular dystrophy, this may put them at higher risk for fractures secondary to diffuse osteopenia. If there is a history of osteogenesis imperfecta (OI), these children are at much higher risk for fractures, even with minor injuries.

Physical Exam

A focused physical exam should always be performed regardless of the chief complaint. In younger children, this exam can be difficult and may have to be repeated many times after addressing pain and anxiety concerns.

General Appearance

Is the child in obvious discomfort or are they happy and smiling? Are the vital signs stable and are they mentating normally? If they are up and walking around, how are they walking? If they are lying in bed, how are they positioned? Children will generally lay in the position of most comfort, so if they are lying with the hip slightly flexed and externally rotated, this could be concerning for a septic joint. If they're limping, are they putting weight on the inside or outside of the foot (which may suggest a foreign body or puncture wound)? 

Inspection

Look at the affected extremity and compare it to the unaffected one. Are there overlying areas of bruising, swelling, erythema, or obvious deformities? Always remember to have the child either dressed in a gown or just in their diaper, as a lot of information can be lost if they are left fully clothed.

Palpation

Start with the unaffected extremity first, as that the child will likely become more difficult to assess once the affected leg is manipulated. Are there any focal areas of tenderness? Palpation of the entire length of the tibia in one-two cm increments should be done if there is concern for a toddler's fracture. Having the parents palpate the child's leg while you observe for a reaction may be helpful for the scared/nervous kid who cries whenever being approached by an examiner. Always remember to palpate pulses and check for capillary refill in areas distal to the injury, in this case dorsalis pedis and capillary refill in the toes, to evaluate for vascular compromise following an injury.

Range of Motion (ROM)

As with palpation, this should be done on the affected extremity last. Will the child actively range their joints when asked or are they resistant? If they are resistant, will they let you or the parents range them passively (i.e. a child with transient synovitis may not show active ROM but will allow hip to be ranged passively, whereas the child with a septic joint will not allow for either active or passive ROM)? In older children/teenagers, check for joint laxity with varus and valgus stress maneuvers. The presence of laxity can suggest MCL and/or LCL tears, while laxity with anterior or posterior drawer testing can be indicative of ACL or PCL tears.

Gait Analysis

If able, the child should get up and attempt to walk while the examiner evaluates gait. This is best done in a hallway or somewhere else outside the small confines of the exam room. In younger children it may be helpful to place them away from their parents, making them more likely to walk to mom or dad. Pay attention to where the child is placing their feet (on the heel, tiptoes, lateral or medial)? Do they appropriately flex at the knee and hip? Do they immediately abandon all attempts and simply drop down and crawl? For the non-ambulatory child, have the parents (or the examiner) hold them upright over the bed or the floor. Will they put equal weight on both legs, or still hold the affected extremity in flexion?

X-rays will almost universally be obtained for every child who presents with a limp, regardless of if they have a fever or not, to rule out fracture or other traumatic injury. Deciding which x-rays are most appropriate can be difficult, especially in small children as they cannot always verbalize and localize areas of pain. Oftentimes the entire affected extremity needs to be radiographically evaluated. For simple injuries (i.e. foreign body to the foot), a foot x-ray should suffice, however for injuries to the bigger bones, such as the tibia and femur, then the joint above and below may have to be imaged as well. If there is concern for hip pathology, then an anteroposterior and frog leg lateral pelvis x-ray is more beneficial than films of just the affected hip. By imaging both hips it allows for comparison to exclude normal variants as well as evaluate for disease processes that can affect both hips like SCFE, avascular necrosis, Legg-Calve-Perthes disease. Additional views, rather than just anteroposterior and lateral views may be necessary depending on what injury concerns exist (i.e. obtaining an oblique tibia/fibula x-ray if there is a concern for a Toddler’s fracture). Note that initial x-rays may be initially read as negative, as some minor injuries (occult toddler’s fracture, stress fracture) may not be seen and may only be evident on follow up imaging seven-ten days later after healing has begun. In febrile children,     x-rays can help to identify joint effusions and show changes associated with osteomyelitis, with the caveat that these images may still be negative until one-two weeks into the illness. With malignant processes, one may see periosteal reactions, primary bony tumors, or metaphyseal changes (leukemic lines).

If there is a concern for an infectious process, ultrasounds of the affected joint are oftentimes indicated for evaluation of joint effusions. Ultrasound can also be helpful in identifying non radio-opaque foreign bodies (plastic, glass, splinters) that may not be seen on initial x-rays. MRI can be used to further evaluate osteomyelitis, bony abscess, or soft tissue changes.  

Bloodwork is also very useful for infectious or inflammatory conditions and is rarely indicated for traumatic injuries, unless there is evidence of more systemic trauma. Typically a CBC, sedimentation rate (ESR), CRP, and blood cultures are useful. It is important to use this lab work to utilize the Kocher Criteria while differentiating between a septic joint and transient synovitis.

Kocher Criteria for Septic Arthritis

If joint aspiration is performed, fluid should be sent for cell counts (> 50,000 WBCs is concerning for infection), gram stain, and culture.

Treatment for most traumatic injuries will consist of either splinting or casting the affected injury sight depending on imaging results and the extent of the injury. Open fractures, extremities with neurovascular compromise, or any concerns for impending compartment syndrome need emergent orthopedic consultation and intervention. Ankle or knee sprains often just require an ACE wrap, air splint (ankle), or knee immobilizer. Foot sprains on minor fractures may necessitate a post-operative (rigid soled shoe) or fracture boot. Tibia/fibula fractures, if not displaced or angulated, may simply require a cast. However, displaced or angulated fractures in skeletally immature children typically will require closed reduction (either in the operating room, or under conscious sedation in the ED) prior to placement of a cast of splint. These types of fractures in older teenagers may require operative intervention. Treatment of SCFE usually requires placing a pin through the affected hip/femoral head, and most of the time the same will be done on the opposite side.

Treatment for infectious causes will depend on which part of the extremity is infected. A septic joint will typically require a thorough washout in the operating room followed by IV broad spectrum antibiotics that may be tailored once culture results are back. Osteomyelitis may just require IV antibiotics unless there are signs of a periosteal or surrounding soft tissue abscess necessitating operative intervention (drainage, debridement). Depending on the clinical course, these children are often transitioned to oral antibiotics to take longer-term, with treatment length determined on a case by case basis.

• Always take a complete history and do a thorough physical exam focusing on more than just the affected extremity.
• Have the child walk - take them out into the hallway and not just the room to capitalize on open space.
• Have the parents perform ROM and palpation if the child is anxious or fearful.
• Evaluate the affected extremity last, as doing it early may interfere with the rest of your exam.
• An adequate exam may require multiple attempts after pain and anxiety has been addressed.
• Remember that indications for more emergent intervention (open fracture, neurovascular compromise, compartment syndrome, septic shock, etc.) should ALWAYS be quickly identified and addressed.

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2. Herman MJ, Marinek M. The Limping Child. Pediatrics in Review. 2015 May.
3. Kost S. Limp. Textbook of Pediatric Emergency Medicine. Lippincott Williams & Wilkins. 2006.
4. Payares-Lizano M. The Limping Child. Pediatr Clin N Am. 2020 Feb.