A review of the clinical records of all outpatients presenting the Rheumatology Unit of Prato, Italy, isolated knee monoarthritis observed over a six-year period revealed that the knee arthritis was associated in five patients with non-small cell lung cancer.

Study participants were all middle-aged men who had been heavy smokers for most of their lives. Knee arthritis, which was very mild, was the first sign of as yet undiagnosed non-small cell lung cancer in the study participants.

However, in every case, the lung cancer was operable and once the cancerous tissue had been removed, the knee symptoms subsided, explained Fabrizio Cantini, of the Hospital Misericordia a Dolce, in Prato, Italy.

Non-small cell lung cancer is particularly difficult to treat unless caught early and in more than half of the cases diagnosed the disease is advanced.