HISTORY.-on March 20, 1939, W. D., a mill worker, aged 28, consulted the author concerning a disability of his right knee-joint. He stated that about 2.0 a.m. on March 16, four days previously, when pulling slabs off a chain, he slipped and his right knee gave out sideways. As far as he could tell, his knee was in a little flexion. At that moment, a slab, weighing probably 8 lb., fell from the chain and landed precisely over the lateral aspect of the right knee-joint. He states that the knee swelled up a little, but he carried on with some difficulty. He worked the next shift at another job, having rubbed the knee with liniment and bandaged it. At the end of this period he was unable to carry on. He stated that the knee had so stiffened that he was unable to move it.
The man's story was checked with his employers', and it was ascertained that he had worked for them for nearly a year at a rather heavy job which required a certain degree of agility. He had proved to be a conscientious workman and had made no complaint of disability. The man himself stated that he had had no previous trouble with this knee.
ON EXAMINATION.-When examined, one noted over the outer side of the knee-joint, and probably posterior to the external lateral ligament, and in front of the biceps tendon, a definite cystic swelling which appeared to be very tender. It was about the size of a hazel-nut. It seemed to disappear on extension and rightangled flexion and was most prominent in semiflexion. There was no fluid demonstrable in the knee-joint, but there was pain on forced lateral movement with the leg in extension. There was no limitation of movement, but pain was complained of on complete extension or flexion.
On March 20, the day of the first consultation, an X-ray examination was made and antero-posterior and lateral views were taken. In these no sign of injury and no abnormal condition was seen.
On March 29 the cystic mass was aspirated under local anmthesia and clear mucoid material was withdrawn with difficulty through a size 17 needle. The swelling was not decreased in size and was still very tender.
A diagnosis of cyst of the external semilunar cartilage of the right knee-joint was made, but in view of the apparent rapid development of this cyst, an orthopzdic confrere, Dr. Boucher, was asked to see this patient. By April 12 no improvement was noted as the result of conservative treatment, and exploratory arthrotomy was agreed upon. He had been seen by a medical officer of the Workmen's Compensation Board shortly after the first consultation, and the findings were there also confirmed.
AT OrERATIoN.-on April 21, 1939, at the Vancouver General Hospital, the author explored the lateral knee-joint, approach being made in front of the external