Presentation
Painful swollen left knee
Patient Data
AP & lateral views.
Periarticular soft tissue swelling and distended suprapatellar bursa.
Mature and multi-layered periosteal new bone along the femoral, tibial and fibular shafts.
Well circumscribed lytic lesion in the medial femoral condyle.
Scanogram: diaphyseal periosteal new bone is bilateral and symmetrical.
CT: well-circumscribed lytic lesion in the medial femoral condyle with destruction of the subchondral bone plate. HOA poorly seen on soft-tissue window.
SPECT: marked increase in bone turnover surrounding the lytic lesion and minor increase in bone turnover in the periosteum.
Right middle lobe bronchus occluded by a mass. Distal drowned airways, collapse and consolidation. Within the collapsed middle lobe is a necrotic mass causing the fissures to bulge.
Right hilar and mediastinal lymphadenopathy.
Expanded lytic left rib lesion.
Right adrenal mass.
Case Discussion
Primary adenocarcinoma was diagnosed by lung biopsy - stage IVb due to multiple extra-thoracic metastases (bone and adrenal). Metastatic destruction of the subarticular medial femoral condyle is the likely cause of his acute knee pain.
Layered periosteal new bone is typical of hypertrophic osteoarthropathy, a recognized paraneoplastic effect of lung cancer.
Omission errors and satisfaction of search: Initially it was assumed that the pain was due to HOA or inflammation in the knee joint. The metastasis was missed due to failure of perception (omission error) and the presence of multiple abnormalities (satisfaction of search).
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