This pilot study explored the use of tensiometry as a measure of retention of knot tying skills. Medical students learned a one-handed square knot tying technique. Their final performances were video recorded and these videos were uploaded on to a website. Students were divided into two groups: an observational learning group that had access to videos before a retention test, and a control group that did not. After a two-week retention period, all students came back and performed one more trial to test the amount of retention of the skill. Tensiometry was used to measure strengths of the knots before and after the retention period. The scores showed no significant difference between the groups (p>0.308) or tests (p>0.737). We interpret the results to suggest that tensiometry is not sensitive enough to detect degradation in the performance of fundamental clinical skills as they are forgotten after being taught.