A prosthetic glenoid component (10, 10') comprising: a body having a concave bearing surface (30, 30') and a glenoid contacting surface, a first peg (22, 22') extending outwardly from the glenoid contacting surface of the body, the first peg (22, 22') having a first length from the glenoid contacting surface to a free end of the peg (22, 22'), a first portion of the first length with a first diameter at the glenoid contacting surface extending for a second length and a second portion with a second diameter extending from the first portion for a third length to the free end of the first peg (22, 22'); and a second peg (16, 16') extending outwardly from the glenoid contacting surface, the second peg (16, 16') having a fourth length from the glenoid contacting surface to a free end of the second peg (16, 16') and a first portion of the fourth length with a first diameter and a second portion of the fourth length with a second diameter, the second portion of the second peg (16, 16') extending to the free end of the second peg (16, 16'); a third peg (18, 18') extending outwardly from the glenoid contacting surface intermediate the first (22, 22') and second (16, 16') pegs, the third peg (18, 18') having a third diameter greater than the second diameter of the first peg second portion and a fifth length greater than the second length of the first peg first portion, wherein: the first diameter of the first and second pegs is larger than the second diameter of the first and second pegs, the third diameter of the third peg is larger than the second diameter of the first and second pegs (22, 22', 16, 16'), and the fifth length of the third peg (18, 18') is less than the first length of the first peg (22, 22'), the prosthetic glenoid component further comprises a fourth peg (20, 20') extending outwardly of the gleonid contacting surface, the first (22, 22') and fourth (20, 20') pegs having central longitudinal axes (38, 38') which are parallel and coplanar along a first plane (50, 50'), the second (16, 16') and third (18, 18') pegs having central longitudinal axes (37, 37'; 40, 40') which are parallel and coplanar along a second plane (54, 54'), characterised in that the fourth peg (20, 20') is adjacent a distal end of the bone contacting surface, that the second plane (54, 54') is perpendicular to the first plane (50, 50'), and that the central axis (37, 37') of the second peg (16, 16') is parallel and coplanar with the central axes (38, 38'; 40, 40', 140) of the first and third pegs (22, 22'; 18, 18', 180). a body having a concave bearing surface (30, 30') and a glenoid contacting surface, a first peg (22, 22') extending outwardly from the glenoid contacting surface of the body, the first peg (22, 22') having a first length from the glenoid contacting surface to a free end of the peg (22, 22'), a first portion of the first length with a first diameter at the glenoid contacting surface extending for a second length and a second portion with a second diameter extending from the first portion for a third length to the free end of the first peg (22, 22'); and a second peg (16, 16') extending outwardly from the glenoid contacting surface, the second peg (16, 16') having a fourth length from the glenoid contacting surface to a free end of the second peg (16, 16') and a first portion of the fourth length with a first diameter and a second portion of the fourth length with a second diameter, the second portion of the second peg (16, 16') extending to the free end of the second peg (16, 16'); a third peg (18, 18') extending outwardly from the glenoid contacting surface intermediate the first (22, 22') and second (16, 16') pegs, the third peg (18, 18') having a third diameter greater than the second diameter of the first peg second portion and a fifth length greater than the second length of the first peg first portion, the first diameter of the first and second pegs is larger than the second diameter of the first and second pegs, the third diameter of the third peg is larger than the second diameter of the first and second pegs (22, 22', 16, 16'), and the fifth length of the third peg (18, 18') is less than the first length of the first peg (22, 22'), the prosthetic glenoid component further comprises a fourth peg (20, 20') extending outwardly of the gleonid contacting surface, the first (22, 22') and fourth (20, 20') pegs having central longitudinal axes (38, 38') which are parallel and coplanar along a first plane (50, 50'), the second (16, 16') and third (18, 18') pegs having central longitudinal axes (37, 37'; 40, 40') which are parallel and coplanar along a second plane (54, 54'), characterised in that the fourth peg (20, 20') is adjacent a distal end of the bone contacting surface, that the second plane (54, 54') is perpendicular to the first plane (50, 50'), and that the central axis (37, 37') of the second peg (16, 16') is parallel and coplanar with the central axes (38, 38'; 40, 40', 140) of the first and third pegs (22, 22'; 18, 18', 180).