Electromagnetic tracking system (ETS). A) ETS instrumentation. B) ETS sensor taped over the sacrum with double sided tape and medical adhesive tape. C) ETS sensor attached to a mouldable plastic plate and tightly wrapped around the lateral aspect of the thigh. Standardized force was applied by a modified hand-held load cell system. D) ETS sensor taped over the medial aspect of the knee with double sided tape and medical adhesive tape.