Joint rupture following internal derangement of the knee.

While playing rugby a 22 year old man sustained a rotational injury during flexion, to his left knee. Before this event, to his knowledge, his knee had been normal; and there was no clinical evidence of arthritis. That evening he noticed his knee had become painful and swollen. One week later, after going for a swim (crawl stroke), he found that the swelling in his knee had lessened and he had developed a swollen calf. Shortly after he was seen at this hospital where he was found to have an effusion in the knee, swelling and pitting oedema of the calf and ankle. There was no popliteal cyst to be felt or other clinical abnormality in the knee joint. No bruising was evident around the lower leg. Twenty mIs. of straw-coloured fluid were aspirated and