Hot Seat Case #133: 22mo M with knee pain
Posted on: June 6, 2019, by : Nate Jones
Nate Jones, MD Children’s National Medical Center
HPI: Patient is a 22 month old male who presents with concerns of knee pain. Per mother, patient has had episodes of intermitted knee pain over the past 5 months. The knee pain appears to be isolated to the left knee and is associated with inability to bear weight and swelling. Episodes typically occur 1-2 times a month, lasts for 1-2 days and self-resolves. Mother in the past has treated it with Tylenol or Motrin. Today patient was brought in due to increased pain and swelling over the past 3 days. No prior workup has ever been done.
ROS:
CONSTITUTIONAL: +/-
tactile fever , no chills, night sweats, weight loss, recent illnesses
SKIN: no rash, no hives, no abrasions
EYES: no pain, no redness, no discharge
ENMT: no sore throat, no nasal congestion
RESPIRATORY: no SOB, no cough
CV: no CP, no palpitations, no syncope
GI: no abd pain, no N/V/D
GU: no dysuria, no hematuria
MSK: +left knee pain, + left knee
swelling , +limp
HEME: no
known bleeding disorder, no easy bruising,
no petechial, no purpura,
NEURO: No HA, no seizures, no altered LOC
PMHx: Born FT NSVD without complications. No other medical issues. Immunizations UTD.
FHX: No h/o bleeding disorders, arthritis, auto immune disorders
SHx: lives at home with parents, not in daycare, no other caretakers.
PE
T 36.7 HR 112 RR 22 100%
Gen: Well appearing
HEENT: NC/AT, PERRLA, EOMI, TM clear b/l, nares clear w/o rhinorrhea, OP clear without erythema , exudates or ulcerations.
Neck: Supple with FROM, no LAD
CV: RRR, S1, S2 without m/r/g
Lung: CTAB without w/r/r
Abd: Soft, NT/ND, +BS , No HSM or masses palpated
EXT: FROM of hips, knees and ankles. No joint swelling, erythema or signs of trauma. No tenderness
Neuro: Awake, alert and interactive. 5/5 strength in all ext. Sensation intact throughout.
Labs/Imaging:
WBC: 9/ Hgb: 9.9/ Hct 32/Plt 378/MCV 61
ESR: 27 CRP 2.04
XR Left Knee:
FINDINGS:
Bones: Normal
Joint alignment: Normal
Joint fluid: None
Soft tissues: Normal
IMPRESSION:
Normal left knee radiographs.
XR Pelvis:
Findings:
Bones: Normal
Hip alignment: Normal
Soft tissues: Normal
IMPRESSION:
Normal radiographic study of the pelvis.
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This is an interesting case! What I find the most challenging is the chronic nature of the symptoms with reported acute worsening, but a normal exam. I would ask in the history for timing of the swelling/pain, ie morning vs. does it happen at any time during the day. One important thing not included in the exam is whether the child’s gait is normal. Bottom line, this is a child with intermittent episodes of monoarthritis for 5 months. The question then becomes how much or how little to do in the ED. This patient has had no work-up done so far and I’m impressed with the story of swelling and pain to the point of inability to bear weight, which would push me to obtain some studies.
From a differential perspective, I would consider infectious, rheumatologic and oncologic etiologies. Under the ID bucket, Lyme arthritis would be highest on my differential. The knee is the most common joint affected in this late manifestation of Lyme disease. It often presents without other constitutional symptoms. The knee can be impressively swollen without significant pain (a good thing to remember when you are trying to figure out whether to be worried about septic arthritis). Osteomyelitis is possible, although the completely normal exam of the leg makes osteomyelitis less likely overall in my mind given the time course. In young children, the initial symptoms can be vague and mild, then progress over time. It is unclear whether this child has been having fevers. That being said, fever is often not present at initial presentation (in a large systematic review of children with acute or subacute osteomyelitis, only 62% had fever at presentation). Other infectious causes such as ARF, post-streptococcal reactive arthritis, cellulitis or transient synovitis are less likely given the clinical hx. In the rheumatologic bucket, I would include oligoarticular JIA. The chronic and intermittent nature of the symptoms would support this dx (although technically should have symptoms for 6 months and rule out other diseases). It is most common in toddlers and young children and most often not associated with other constitutional symptoms. On exam, I was taught by a rheumatologist that the knee should never feel warmer to touch then the thigh or lower leg. If warmer, it is suggestive of inflammation of some sort. Oncologic causes remain to be considered (bone tumor, leukemia), although the history does not seem to support this as much and the lack of constitutional symptoms is reassuring. Overall, given all this, I would obtain CBC w/ diff, ESR, CRP, blood cx (important for identifying a potential organism for osteomyelitis) and Lyme testing. I would obtain xrays of the knee – r/o bone tumor and should see changes related to osteomyelitis given the 5-month history of symptoms. Given the normal knee exam without effusion, I don’t think an ultrasound of the knee would be helpful. I typically will obtain one if I am considering tapping the knee. I see no indication to do so at this time. Based on the lab results and normal xrays, I would feel comfortable not calling any consult in the ED and discharging home with close PCP f/u and possible referral to Rheumatology if Lyme testing is negative. Looking forward to hearing other people’s thoughts!