While haemarthrosis is a common finding in severe factor VIII or IX deficiency, it is unusual in mild coagulation factor deficiencies. We describe three patients with mild factor IX, X or XI deficiency who presented with spontaneous haemarthrosis. All underwent joint puncture with subsequent worsening of the haemarthrosis in the affected joint. This report indicates that: (i) even mild coagulation factor deficiency may be associated with haemarthrosis; (ii) patients with suspected haemarthrosis should undergo routine screening coagulation tests before joint puncture; and (iii) any abnormalities in the screening tests indicate a need for further evaluation of the coagulation status. In such cases puncture of the joint should be deferred and specific therapy started immediately.