A suture anchor comprising: a cannulated non-expandable body comprising: a distal end having a first portion and a second portion; a proximal end configured to engage a suture anchor insertion instrument; a plurality of projections extending, radially, from an outer surface extending between the distal end and proximal end, the plurality of projections configured to compress into bone; an expandable cap defining a cavity configured to engage the distal end of the cannulated non-expandable body, the cavity having a diameter larger than the first portion and smaller than the second portion that allows the expandable cap to expand radially outward and compress into the bone during engagement of the distal end of the cannulated nonexpandable body and the expandable cap; and a suture extending from the cavity of the expandable cap and slidably received within the cannulation of the non-expandable body; wherein the non-expandable body and the expandable cap each comprise complementary engagement features configured to mechanically engage with each other to lock the non-expandable body and the cap together and to inhibit the expandable cap from returning to an unexpanded state, wherein the expandable cap further comprises a terminal surface adjacent the cavity defining a first aperture, a second aperture, and a bridge separating the first aperture and the second aperture; and wherein the suture extends around the bridge, and a first free end and a second free end of the suture are routed through the first aperture and second aperture, respectively, and through the cannulation of the non-expandable body toward the proximal end of the cannulated non-expandable body. a cannulated non-expandable body comprising: a distal end having a first portion and a second portion; a proximal end configured to engage a suture anchor insertion instrument; a plurality of projections extending, radially, from an outer surface extending between the distal end and proximal end, the plurality of projections configured to compress into bone; a distal end having a first portion and a second portion; a proximal end configured to engage a suture anchor insertion instrument; a plurality of projections extending, radially, from an outer surface extending between the distal end and proximal end, the plurality of projections configured to compress into bone; an expandable cap defining a cavity configured to engage the distal end of the cannulated non-expandable body, the cavity having a diameter larger than the first portion and smaller than the second portion that allows the expandable cap to expand radially outward and compress into the bone during engagement of the distal end of the cannulated nonexpandable body and the expandable cap; and a suture extending from the cavity of the expandable cap and slidably received within the cannulation of the non-expandable body; wherein the non-expandable body and the expandable cap each comprise complementary engagement features configured to mechanically engage with each other to lock the non-expandable body and the cap together and to inhibit the expandable cap from returning to an unexpanded state, wherein the expandable cap further comprises a terminal surface adjacent the cavity defining a first aperture, a second aperture, and a bridge separating the first aperture and the second aperture; and wherein the suture extends around the bridge, and a first free end and a second free end of the suture are routed through the first aperture and second aperture, respectively, and through the cannulation of the non-expandable body toward the proximal end of the cannulated non-expandable body. <EOS>