A passively activated safety needle assembly comprising: an elongate, hollow outer shield having a distal end, a proximal end, an outer surface, an inner surface, and an aperture that permits a needle to extend therethrough; an elongate hub having a distal end and a proximal end, the hub slidably engaged with the outer shield; a spring element positioned within the elongate, hollow outer shield adjacent the proximal end of the elongate hub, which causes the outer shield to slide proximally with respect to the hub; and the needle extending from the proximal end of the elongate hub within the spring element and the outer shield such that proximal movement of the hub with respect to the outer shield compresses the spring element and causes the needle to project through the aperture; characterized in that the elongate, hollow outer shield comprises an activation element protruding inwardly from the inner surface, and at least one finger biased radially inwardly; the hub includes a longitudinal groove that guides the activation element during relative sliding motion between the hub and the outer shield; and the hub comprises a locking ring having a ring element complementary to the activation element and at least one ramped surface radially spaced from the ring element and providing a proximal facing edge, wherein distal movement of the outer shield with respect to the hub causes the activation element and the ring element to rotate the locking ring such that the at least one finger aligns with the ramped surface and subsequent proximal movement of the outer shield causes the at least one finger to engage the proximal facing edge, preventing further relative movement of the outer shield and the hub. an elongate, hollow outer shield having a distal end, a proximal end, an outer surface, an inner surface, and an aperture that permits a needle to extend therethrough; an elongate hub having a distal end and a proximal end, the hub slidably engaged with the outer shield; a spring element positioned within the elongate, hollow outer shield adjacent the proximal end of the elongate hub, which causes the outer shield to slide proximally with respect to the hub; and the needle extending from the proximal end of the elongate hub within the spring element and the outer shield such that proximal movement of the hub with respect to the outer shield compresses the spring element and causes the needle to project through the aperture; characterized in that the elongate, hollow outer shield comprises an activation element protruding inwardly from the inner surface, and at least one finger biased radially inwardly; the hub includes a longitudinal groove that guides the activation element during relative sliding motion between the hub and the outer shield; and the hub comprises a locking ring having a ring element complementary to the activation element and at least one ramped surface radially spaced from the ring element and providing a proximal facing edge, wherein distal movement of the outer shield with respect to the hub causes the activation element and the ring element to rotate the locking ring such that the at least one finger aligns with the ramped surface and subsequent proximal movement of the outer shield causes the at least one finger to engage the proximal facing edge, preventing further relative movement of the outer shield and the hub.