Bruising: a useful physical sign in ruptured knee joint.

The clinical distinction of a ruptured knee joint or popliteal cyst from a deep venous thrombosis is important in the planning of treatment, particularly to avoid anticoagulant therapy. Bruising, which may be severe, may occur when inappropriate anticoagulants are administered. It is less well recognised that spontaneous bruising may occur with a ruptured knee joint even when anticoagulant therapy has not been given. A case is presented which demonstrates this useful physical sign and shows also the value of the patient's history in eliciting the diagnosis. The bruising extended to the foot, its gravitational and propulsive advance being halted by the pressure of footwear. This appearance has not been emphasised in the rheumatology literature.