Valgus arthritic deformities commonly present with tightness of lateral soft-tissue structures which may be associated with varying degrees of laxity of the medial structures. Contracture of the iliotibial (IT) band, popliteus tendon, posterolateral capsule and popliteofibular ligament may be encountered in these knees (Fig. 4.1). We do not believe that the lateral collateral ligament (LCL) undergoes contracture and shortening. The surgeon should be aware which soft-tissue structures are taut in different positions of knee flexion and extension so that a calibrated, stepwise approach is followed during release and imbalance or instability avoided. Essentially, the LCL and popliteus tendon are taut in both flexion and extension, the IT band and posterolateral capsule are taut only in extension, and the popliteofibular ligament is taut only in flexion [3].

In addition, there may be asymmetric wear or hypoplasia of the posterior condyles with excessive wear of the posterolateral condyle of the femur and/or tibia (Fig. 4.2a, b) [4]. This is important to note intraoperatively as using the posterior femoral condyles as a reference to place the AP cutting block may cause excessive resection from the posterior femoral condyle laterally, thereby resulting in excessive internal rotation of the femoral component and patellar maltracking. Using the AP axis (as described by Arima and Whiteside [5]) as an alternative to achieving proper femoral component rotation is also fraught with risk especially if the patella is maltracking and leads to more lateral wear of the trochlear groove (Fig. 4.2c). Hence, the transepicondylar axis (TEA) is preferred by the authors in severe valgus deformities as a landmark for determining femoral rotation. Patellar maltracking, commonly seen in severe valgus deformities (Fig. 4.2a), is usually the consequence of an excessive Q angle due to valgus malalignment, excessive external tibial torsion and excessive tightness of the lateral retinaculum [6]. Valgus knees may also be associated with external rotation deformity of the proximal tibia due to a tight iliotibial tract [6]. Lastly, the valgus arthritic knee just like the varus knee may also be associated with a sagittal plane deformity such as flexion or hyperextension deformity or an extra-articular deformity which may further complicate the surgical technique. Most patients with a valgus deformity at the knee have associated hindfoot valgus (flatfeet) (Fig. 4.3) and even distortion of the midfoot [7, 8]. The authors have reported that despite restoring the hip-knee-ankle (HKA) axis in such patients, the ground mechanical axis may still pass lateral to the centre of the knee joint, and this may need to be factored in while deciding what should be the final knee alignment during TKA [7].

Valgus knees form a spectrum of deformities with important differences which impact surgical technique. All valgus knees are not alike! Ranawat et al. [9] had classified valgus arthritic knees into three major variants based on the degree of deformity, status of medial collateral ligament (MCL) and the amount of lateral release required – variant 1 showing minimal valgus deformity and medial soft-tissue stretching; variant 2 showing substantial deformity (>10°), bone loss and medial stretching; and variant 3 showing severe deformity and osseous deficiency with an incompetent medial soft-tissue sleeve. The authors have modified this classification to include six types of valgus knees based on (1) severity and correctibility of valgus deformity, (2) associated flexion, hyperextension or extra-articular deformity and (3) status of the medial collateral ligament (MCL) (Table. 4.1, Figs. 4.4, 4.5, 4.6, 4.7, 4.8 and 4.9).