Endoprosthesis for the knee joint

An expandable bone prosthesis comprising:

• a first component having a joint part thereon;
• a second component having a joint part at one end thereof, said second component having a telescoping stem extending from said joint part thereof for attachment to a bone, said telescoping stem having an inner member and an outer member axially adjustable with respect to one another by means of a threaded spindle fixedly attached to one of said inner and outer members and a threaded spindle nut fixedly attached to the other of said inner and outer members;
• a pinion means attached to one of said threaded spindle or spindle nut for rotation therewith;
• an indexing means for rotating said pinion means a predetermined amount upon movement of said joint components towards one another after implantation, said indexing means includes a pin which is spring mounted on said second component, said pin having a first end engageable with a surface of said first component and a second end for engaging teeth on said pinion upon engagement of said first end with said first component surface upon said movement of said joint components towards one another;
• and
• a spring-loaded locking pawl is provided coacting with the teeth on said pinion which pawl rotates the pinion a further predetermined distance when the indexing pin disengages the teeth.