Anterior cruciate ligament substituting knee implants

A knee prosthesis that is configured to articulate between a substantially extended position and a flexed position, the knee prosthesis comprising:

• a femoral component including a medial condyle having a medial wall and a lateral condyle having a lateral wall, the medial and lateral walls defining a substantially triangular shaped opening therebetween;
• and
• a tibial component including:
• a medial surface sized to receive the medial condyle of the femoral component;
• a lateral surface sized to receive the lateral condyle of the femoral component;
• and
• a central eminence extending proximally from the tibial component and configured to project between the medial and lateral walls, the central eminence having at least a portion that has a substantially triangular cross-section to engage the substantially triangular shaped opening and prevent relative rotation between the tibial and femoral components in the substantially extended position.

A knee prosthesis that articulates between a substantially extended position and a flexed position, the substantially extended position defined as including full extension up to approximately 20° of knee flexion, the knee prosthesis comprising:

• a femoral component including a medial condyle having an inner medial wall and a lateral condyle having an inner lateral wall, the inner medial and lateral walls being substantially flat to define a substantially triangular shaped opening therebetween;
• and
• a tibial component including:
• a medial surface configured for contact with at least a portion of the medial condyle of the femoral component;
• a lateral surface configured for contact with at least a portion of the lateral condyle of the femoral component;
• and
• a central eminence extending proximally from the tibial component and projecting between the medial and lateral condyles of the femoral component in both the substantially extended position and the flexed position, the central eminence having less contact with the inner medial and lateral walls when the knee prosthesis is in the flexed position than when the knee prosthesis is in the substantially extended position such that the femoral and tibial components are more constrained, due to contact between the central eminence and the inner medial and lateral walls, against movement relative to each other when the knee prosthesis is in the substantially extended position than when the knee prosthesis is in the flexed position.