**4. Management of deformities**

#### **4.1. Varus deformity**

During the arthritic course, there are expected modifications in native alignment and ligament function. Loss of cartilage can create an asymmetrical compartment balance, leading to contracture of soft tissues on the concave side and contralateral loosening on the convex side. As the deformity progresses, these modifications tend to establish into fixed deformities. In varus knees, contraction of medial side involves medial collateral ligament and the whole medial periosteal sleeve, including hamstrings, posteromedial capsule, and PCL. As the deformity progresses, the lateral compartment becomes insufficient, causing abnormal lateral opening and instability.

**4.2. Valgus deformity**

augmentation and more constrained implants.

In the valgus knee, the lateral structures contract, while the medial soft tissues stretch. Differing from varus knees, where the bone erosion occurs more in the tibial bone, in valgus knees most of the bone deformity comes from the femoral side (**Figure 13**). As the deformity

**Figure 12.** In advanced deformities, when there is great medial bone loss, the surgeon must consider using metal

Planning Primary Total Knee Arthroplasties http://dx.doi.org/10.5772/intechopen.72775 15

Lateral soft tissue structures, including the lateral collateral ligament (LCL), iliotibial band (ITB), and the lateral capsule, contract, while the medial soft tissues stretch. When this

**Figure 13.** Most part of the bone wear occurs on lateral femoral condyle, although it could involve tibial bone as well.

progresses it tends to involve the tibial bone and cartilage as well.

Instability of the arthritic knee may be viewed as symmetrical or asymmetrical. Symmetrical instability is seen during early arthritis, when there is erosion of cartilage or bone without associated adaptive soft tissue changes. During physical examination, the deformity can be corrected under active reciprocal stress on physical examination. This kind of instability is easily corrected during surgery without needing extensive ligament releasing.

As the deformity progresses it tends to turn into an asymmetrical instability, which is not corrected by active reciprocal stress during physical examination. This kind of fixed deformity occurs when cartilage and bone loss lead to adaptive ligamentous changes. In order to correct this kind of deformity, ligamentous release is mandatory, turning a trapezoidal gap into a rectangular gap. In asymmetrical instabilities, the bone cuts alone are not sufficient to accomplish articular balance.

Instead of only releasing ligaments from the contracted concave side someone could advocate to advance ligament complexes on the convex side, especially when the opposing ligaments are stretched to the point of being incompetent. These authors do not favor ligament advances or reconstructions on the convex side since the functional outcomes have not been acceptable in most series. In such cases, the authors advise considering a more constrained knee design (**Figure 12**).

**Figure 12.** In advanced deformities, when there is great medial bone loss, the surgeon must consider using metal augmentation and more constrained implants.
