The Limping Child Module

• The differential is broad at this stage – it includes benign self-limiting conditions such as a minor traumatic soft tissue injury through to more serious conditions such as Perthes disease and Slipped Capital Femoral Epiphysis (SCFE).
• A detailed history should be elicited to rule out the presence of any red flag symptoms that might suggest systemic illness
  • Night pain
  • Weight loss
  • Night sweats
  • Anorexia/general malaise
• The child requires a thorough examination including abdomen, groin and the whole of the lower limb to establish the location of the pathology – remember that hip pain can be referred to the knee.
• X-rays including a pelvis and frog-leg lateral are essential to look for evidence of hip joint integrity.

A thorough history establishes that the child is systemically well but overweight. He has restricted movement in his left hip. You notice that he externally rotates his hip when you try to flex it. This is his x-ray:

• The x-ray findings suggest a slipped capital femoral epiphysis on the left hand side.
• It is a Type I Salter Harris injury affecting the growth plate of the upper femur.
• Triggers include growth spurt (i.e. puberty), obesity and trauma.
• Initial management involves referral to an orthopaedic specialist
  • Must be kept non-weight bearing
  • Likely to need surgery involve pinning of epiphysis
  • Will need ongoing monitoring due to risk of long term problems e.g.
    • Osteoarthritis
    • Avascular necrosis of the femoral head
    • Slipping of the contralateral side (~20% of cases)

• X-ray – mandatory to look for evidence of e.g. Perthes
• Bloods – could be considered as he is still not weight-bearing after analgesia.
  • He is afebrile and systemically well so will likely be normal
  • May be useful for looking for rare causes of limp e.g. initial presentation of leukaemia
• US – depending on availability may be useful to look for a joint effusion. In transient synovitis expect to see a simple joint effusion +/- evidence of thickened and inflamed synovium.

X-ray and baseline bloods including inflammatory markers are normal.

• Most likely to be a transient synovitis
  • Although transient synovitis is more common after a viral illness, it does still occur in children who have been otherwise well recently.
• As long as you are reasonably confident that this child has transient synovitis it may be possible to discharge him with careful safety-netting advice.
• If his pain gets worse or he develops a fever his parents should bring him back to ED promptly for further assessment.
• Some form of review is almost certainly going to be advisable as he is not weight bearing. Depending on local hospital protocol this may be an ED clinic or a paediatric rapid access clinic.

• Tonsillitis gives a source for the fever and the raised infection markers
• It can also act as a source for haematogenous spread of osteomyelitis/septic arthritis
• Staph aureus is one of the most common causes of both tonsillitis and septic arthritis/osteomyelitis

• Children with septic arthritis are likely to be in more pain and have a more limited range of movement and are unlikely to weight -bear.
• They may be systemically unwell.
• Kocher’s criteria may help clarify your level of suspicion
  • A point is given for each of the four following criteria:

• Non-weight-bearing on affected side
• Erythrocyte sedimentation rate >40
• Fever > 38.5°C
• White blood cell count >12,000

• Ultrasound of the hip joint may reveal a complicated effusion.
• The only certain way to know the difference is joint aspiration

• Children with sickle cell disease are functionally asplenic due to recurrent micro-infarcts of their spleens.
• This leaves them at high risk of infection from encapsulated bacteria such as pneumococcus and salmonella.
• Diarrhoea could leave her dehydrated and provoke a painful crisis – as the family fear.
• A history of fever and diarrhoea however, must make the clinician suspicious of salmonella infection with the risk of haematogenous spread.

• She is high risk for systemic bacterial infection so, given her presentation, needs assessing for features of sepsis and shock
• Meticulous examination of her musculoskeletal system to find a focus for the pain.
• Initial management is likely to involve fluids, antibiotics and analgesia.

Examination reveals a painful, hot left ankle with some mild swelling. The child screams in pain when you attempt to move it.  

• Paediatricians
• Haematologists
• Radiologists
• Microbiologists
• Orthopaedic surgeons
• Anaesthetists
• (Critical Care – depending on how unwell she is)

Despite attempts at a thorough history and examination, you are still unsure what the underlying cause for Jame’s pain is. You cannot safety net and discharge him home without further investigations even though you know taking bloods and performing X-rays will be challenging.

You do bloods and an X-ray which again have been a challenging exercise.

Blood results:
Hb   9.8, WCC  15.6, Plt    299, Na  131, K  haemolysed, Urea  2.4. Creat   15
ESR insufficient
LDH haemolysed

James has presented with atraumatic joint pain.

There is a wide-range of aetiologies but most are benign and self limiting. However nestled among these varied presentations are limb and life-threatening infections and non-accidental injuries. Getting a detailed history from an older child with learning difficulties is going to be challenging, as is getting a history from a preverbal child. One should always approach a scenario with a detailed history; and in this case the main aim would be to tease out red flags with the assistance of the parent/caregiver followed by an examination.

History

A systematic structure to history taking is the SOCRATES pneumonic for a pain focused history.

S: Site. Ask the child where it hurts. Children are more likely than adults to experience referred pain. Remember: knee pain emanates from the hip (in 35% of cases). Also pain from the spine can refer to the lateral thigh.

James rubs his right hip region when you ask him where it hurts.

O: Onset. Is the pain acute or chronic? Acute onset tends to be more concerning and suggests joint/bone infection, trauma, or with acute deterioration of a chronic problem. Chronic pain is more suggestive of an inflammatory process, overuse syndromes or an osseous cause such as SUFE or Legg-Calve-Perthes disease. Malignancy often has a delayed presentation with mild dull pain that may not be activity limiting in the initial stages. Nocturnal pain is a red flag and should always be asked about.

James is unable to answer your questions. Mum thinks James has been unwell since Monday (3 days ago), and says he doesn’t have problems sleeping.

C: Character. Dull ache (deep tissue pathology) or sharp sting (cutaneous involvement) can be helpful.

James is unable to answer both questions to character and radiation.

R: Radiation. Can be difficult to elicit exact origin of pain and radiation, especially in the younger child. Be aware of bilateral limb involvement as this may suggest a more central cause, such as cauda equina.

A: Associations.

Weight-bearing: non-weightbearing can suggest more serious pathology

Mono or polyarticular: polyarticular is generally less concerning and suggests an underlying systemic disease process. However, 8% of septic arthritis cases involve more than one joint and leukaemic infiltrates typically affect multiple joints.

Systemic illness: chronic features such as malaise, fatigue, weight loss could suggest underlying increase in catabolism from a systemic disease such as SLE, JIA, or anaemia from malignancy.

Dermatology: extra-articular features of inflammatory bowel disease (IBD) (eye pain, pyoderma gangrenosum, erythema nodosum, aphthous ulcers). Ask the parents about any new marks on the body and later during the examination look for a Salmon patch of juvenile idiopathic arthritis (JIA). Consider whether this presentation is associated with a recent upper respiratory infection or viral gastroenteritis which may be suggestive of reactive arthritis.

Mum says James is off his food but he hasn’t lost weight.

T: Time course. Note the pain progression over time and response to analgesics.

Mum says James is more comfortable after Ibuprofen which she started giving him 2 days ago.

E: Exacerbating or Relieving factors. Trauma and infection aggravate pain after activity and are relieved by rest. The presence of pain that is relieved by activity is more suggestive of an underlying inflammatory cause. Pain relieved with rest is pain from osteochondrosis in the adolescent experiencing growth spurts.

S: Severity. Severity is subjective but a surrogate of severity is the inability to walk or to tolerate examination with distraction.

Finish off the SOCRATES pain history with a FAST history:

F: Family history for autoimmune disease (IBD, psoriatic arthritis)

A: Adolescent screen. The sexually active teenager could present with joint infection due to gonococcus or joint inflammation due to chlamydia. Similarly ask about IV drug use as this increases the chance for infectious arthritis.

S: Safeguarding. Due attention should be maintained for a history that is not in keeping with the presentation or the child’s developmental age.

T: Travel history

Examination

Look. Inspection is non-invasive, interactive and can be used to establish rapport.

Feel for temperature changes, tender areas, effusions.

Move actively and passively with the aim of gently stressing the ligaments of which the joint is comprised.

It is always important to complete a comprehensive general examination especially in the presence of red flags or suspicion of a multisystem disease.

pGALS is a standardised musculoskeletal (MSK) basic examination. Free educational resources to demonstrate pGALS are available online. (www.pmmonline.org).

pGALS screen has the benefit of quickly assessing all joints, this is important given the sometimes vague presentation of MSK problems and the difficulty of localising the site of joint pathology from the history alone. Frequent practice of pGALS, especially on healthy children, is important to appreciate normal ranges of movement as joint ‘restriction’ – a common finding in JIA can be easily missed especially with symmetrical joint disease.

The x-ray is diagnostic and demonstrates a large pelvic Ewing’s sarcoma.

The blood tests (which were very difficult to obtain from James) reveal an anaemia and leukocytosis. A marginally elevated ESR and LDH may also be evident in Ewing’s sarcoma.

Ewing’s sarcoma typically presents with more systemic disease at presentation and localised pain. At diagnosis, the median duration of symptoms is 3-9months.

Any child or adolescent who’s pain involves any of these characteristics should be investigated to exclude a malignant pathology with at least a plain film X-ray.

–        A painful ‘injury’ which fails to resolve over a reasonable time (over 1 month)

–        Intermittent or persistent localised pain for one month with no history of trauma

–        Night pain that wakes you up from sleep or prevents adequate sleep

–        Fracture where history of force resulting in injury seems insufficient

Ewing’s sarcoma occur more commonly in the pelvic bones, diaphysis of the long bones of the leg, and bones of the chest wall.

At presentation 25% will have metastatic disease to the lung, bone or bone marrow or a combination of these.

Plain X-ray in 2 planes of the painful area remains the first line investigation of choice and is readily available to most clinicians. Ewing’s (as well as an osteosarcoma) can lead to a radiologically significant sign – the Codman triangle. It is a triangular area of new subperiosteal bone that is created when a lesion, often a tumor, raises the periosteum away from the bone. Ewing’s sarcoma traditionally demonstrates osteolysis, detachment of the periosteum and occasional calcification in any associated soft tissue mass.

There are no peripheral blood tests or tumor markers which are diagnostic of bone tumors.

Further imaging of the affected bone is required to adequately determine the true extent of the disease and staging.

Biopsy is the gold standard for histological diagnosis.

Whole body technetium-99m bone scans and CT chest are performed to assess metastatic disease at presentation.

Bone marrow aspirates and trephines are required for Ewing’s sarcoma patients as marrow involvement is a part of the disease process and for some high dose procedures requiring harvest of stem cells from the patient may be part of the treatment.

Referrals to a specialist orthopaedic sarcoma surgeon, paediatric oncologist, radiology services, paediatric surgeon, rehabilitative specialists and physiotherapists to name a few are required.

Important to note that although malignancy is rare, it should be actively excluded. Also, blood tests may be normal even in cases of inflammatory, infectious and neoplastic joint pain and peripheral blood films may not show blast cells in children with leukaemia cells.

Which of the following is NOT part of Kocher’s criteria for assessing the risk of septic arthritis in a limping child?

A: ESR >40

B: Range of movement <50% normal

C: WCC > 12×10⁹

D: Fever >38.5^oC

E: Inability to weight bear

The correct answer is B.

Although range of movement can be a useful part of the assessment, it is not part of the official Kocher criteria.

Which of these statements about SCFE/SUFE is TRUE?

A: It is most common in underweight children between the ages of 6-10. It can be a cause of chronic hip pain and is bilateral in approximately 10% of cases.

B: It is a cause of both acute and chronic hip pain, is rarely bilateral and typically occurs in overweight adolescents.

C: It is caused by avascular necrosis of the femoral epiphysis and usually presents as a chronic problem. Radiological detection is improved by requesting a ‘frog-leg lateral’ view.

D: It is most common in children over the age of 10 and can present with acute or chronic pain. It is bilateral in around 20% of cases and radiological detection is improved by a ‘frog-leg lateral’ view.

E: It is a common cause of limp and pain in underweight adolescents and is bilateral in one third of cases. Early detection and referral improves prognosis.

SCFE is most common in boys between the ages of 10-17 with a median age of 13. It is the most common cause of serious hip pathology in adolescents. 50% of them are >95th centile for weight and knee pain is a common initial presentation. Pain and limp may be entirely acute but often presents with an acute on chronic picture with long term low level pain suddenly becoming more acute with a large epiphyseal slip

In a classical antalgic gait, which phase of walking is affected?

A: Strike

B: Contact

C: Stance

D: Propulsion

E: Swing

The correct answer is C.

The stance phase is shortened in an antalgic gait as the patient tries to minimise the amount of time that weight is placed through the painful leg. (https://pemplaybook.org/podcast/please-just-stop-limping/ for diagram of phases of gait and fuller explanation)

Which of the following bacteria is the most likely to cause septic arthritis?

A: E. Coli

B: Streptococcus pneumoniae

C: Haemophilus Influenza B

D: Staphylococcus aureus

E: Salmonella

The correct answer is D.

Although all of the organisms above can cause joint pathology, the most common is Staph aureus. Previous studies suggest it is responsible for over half of all cases of septic arthritis.

Which of the following statements about Perthes disease is FALSE?

A: It is more common in boys than girls

B: It is bilateral in 10% of cases

C: It is defined by avascular necrosis of the femoral head

D: An older age at diagnosis is associated with a more favourable prognosis

E: Physiotherapy, casting and surgery may all form part of the treatment regimen

The correct answer is D.

Perthes disease is five times more common in boys than girls although damage is often more severe in affected girls. It may be bilateral in around 10% of cases and is defined by avascular necrosis of the femoral head. The younger a child is diagnosed the more favourable the prognosis owing to a greater potential for bone remodelling. Children under the age of 6 do especially well. Management is multidisciplinary and physio, casting and surgery may contribute at various stages of the disease process.

A 10 year old presents with an acute onset of right hip and wrist pain following a very minor trip and fall onto the ground. Since the incident she has been unable to bear weight. On examination the right hip and wrist showed no obvious deformity and range of movement were normal after her pain was addressed. During the last 2 years she had not presented to the GP but recently she had complained of poor sleep, leading to daytime somnolence, palpitations, anxiety and sweating. A fall in her weight growth curve was noted after plotting her on a growth chart.

Which statements are FALSE?

A: This is a ‘red herring’ injury commonly reported by patients and their parents and will not require further investigations.

B: For children over the age of 8 years or limping > 7 days an X-ray is an adequate imaging modality as it has a relatively low dose of radiation but is also very likely to show the pathology causing the pain.

C: Blood tests are indicated including thyroid functions because the minor fall is not in proportion to the severity of her symptoms and her unexplained weight loss is of concern

D: Transient synovitis is most common in this age group so cooling, rest and pain relief are adequate therapy.

The correct answers are A and D.

The most common cause for hip pain (in children aged 3-10years) is transient synovitis. Even though this is a benign cause not requiring further treatment, other more severe differential diagnoses need to be considered. A ‘red herring’ injury is commonly reported by patients and their parents but in this case the minor fall was not in proportion to the severity of her symptoms. Similarly, X-ray and blood tests including thyroid functions are indicated due to the red flags of not weight bearing, disproportionate severity of her pain and unexplained weight loss. The indications for a CT scan are limited in this context. In this case, she had a  pathological fracture due to endocrine abnormalities. Hyperthyroidism is rare but a severe disease in children and mostly autoimmune.