A tibial prosthesis comprising: a medial base portion configured to engage a medial surface of a tibia; a lateral base portion configured to engage a lateral surface of the tibia, wherein at least a portion of the medial and lateral base portions are separated by a passage interposed therebetween; and a bridge coupling the medial base portion and the lateral base portion, wherein at least a portion of the bridge is elevated above a portion of the passage between the medial base portion and the lateral base portion, the bridge defining an underlying area that receives at least a portion of a tibial eminence when the tibial prosthesis is engaged with the tibia, wherein a height of the bridge varies in a superior direction across the passage; wherein the medial base portion and the lateral base portion each comprise a lip (126a,126b) formed along a respective mesial edge, wherein each lip increases in height from a posterior portion of the tibial prosthesis to an anterior portion of the tibial prosthesis, the bridge comprising a posterior edge defining a posterior opening, wherein the lips extend to the posterior edge and form, at least in part, the posterior opening, the lips providing support to allow the bridge to accommodate the at least a portion of the tibial eminence, characterised in that the mesial edge of the medial base portion and the mesial edge of the lateral base portion are substantially non-parallel to one another along a majority of an anterior-posterior length of the tibial prosthesis, and wherein a width of the passage between the medial base portion and the lateral base portion increases from the anterior portion of the tibial prosthesis to the posterior portion of the tibial prosthesis. a medial base portion configured to engage a medial surface of a tibia; a lateral base portion configured to engage a lateral surface of the tibia, wherein at least a portion of the medial and lateral base portions are separated by a passage interposed therebetween; and a bridge coupling the medial base portion and the lateral base portion, wherein at least a portion of the bridge is elevated above a portion of the passage between the medial base portion and the lateral base portion, the bridge defining an underlying area that receives at least a portion of a tibial eminence when the tibial prosthesis is engaged with the tibia, wherein a height of the bridge varies in a superior direction across the passage; wherein the medial base portion and the lateral base portion each comprise a lip (126a,126b) formed along a respective mesial edge, wherein each lip increases in height from a posterior portion of the tibial prosthesis to an anterior portion of the tibial prosthesis, the bridge comprising a posterior edge defining a posterior opening, wherein the lips extend to the posterior edge and form, at least in part, the posterior opening, the lips providing support to allow the bridge to accommodate the at least a portion of the tibial eminence, characterised in that the mesial edge of the medial base portion and the mesial edge of the lateral base portion are substantially non-parallel to one another along a majority of an anterior-posterior length of the tibial prosthesis, and wherein a width of the passage between the medial base portion and the lateral base portion increases from the anterior portion of the tibial prosthesis to the posterior portion of the tibial prosthesis.