Swollen Knee (Monoarthritis)
Five year old Meena presents with 6 weeks of leg pain and noted to be stiff in the mornings. She is unable to sit cross legged on the floor at school. Otherwise she is well with no systemic upset and no fever.
pGALS shows swollen knees, right more than the left. Otherwise she is well with no systemic upset. Blood tests from her paediatrician are normal - complete blood count, ESR, CRP. ANA (using Indirect Immunofluorescence) is negative. Chest radiograph is normal and the mantoux test is negative.
Diagnosis - Oligoarticular JIA.
- Prescribed NSAIDS and analgesia.
- Plan admit for intra-articular joint injection under general anaesthetic.
- Refer ophthalmology for eye screening (even though she is ANA negative, she is still at risk of uveitis).
- Attended for joint injections, 2 weeks later - noted to have large effusions both knees which were aspirated and injected with triamcinolone hexacetonide- 1mg/kg/joint. Bloods are repeated whilst under anaesthetic. Complete blood count normal, CRP <5, ESR 16. Varicella serology positive.
- Physiotherapy as an outpatient.
- Eye screening (no uveitis).
The photographs below show a swollen right knee in Oligoarticular JIA.
This child has Oligo-articular JIA.
One third of children with this JIA subtype may develop a polyarticular course (if this happens after 6 months, then it is called Extended Oligoarticular JIA), and warrant systemic immunosuppression (with methotrexate or may progress to a biologic). If varicella negative then varicella vaccination would be recommended in case she needs to have methotrexate in the future. The vaccine would be contraindicated when on methotrexate. Varicella infection can be serious in children who are immunosuppressed.
The photograph below shows zoster infection in a child who is immunosuppressed.