The presence of osteophytes on the medial aspect of the tibial plateau and on the medial femoral condyle can have a significant tightening effect on the structures that make up the medial soft tissue sleeve. For this reason, all osteophytes should be removed before any soft tissue release is performed. Removal of the osteophytes that impede on the medial soft tissue sleeve is often enough to provide a balanced flexion and extension gap in the mild varus knee [5] (Fig. 9.2).

The critical stabilizers on the medial side of the knee include the superficial medial collateral ligament (sMCL) fibers on the anterior aspect and posterior structures such as the posterior oblique ligament (POL) and the semimembranosus (SM) tendon fibers that merge into the posterior capsule [6].

The sMCL has its origin on the medial epicondyle and its tibial insertion on the medial aspect of the upper tibia. It affects both the flexion (anterior fibers) and the extension (posterior fibers) gap. A subperiosteal technique is used to release the sMCL off the tibial insertion from just medial to the pes anserine tendon insertion to the medial aspect of the upper tibia (Fig. 9.3). The surgeon should begin by performing a gentle release and then reassess the flexion and extension gaps so that the appropriate amount of release can be obtained without causing overcorrection or instability resulting from an excessive amount of release.

The POL fibers run in an oblique fashion from the upper posterior aspect of the sMCL fibers into the posteromedial aspect of the medial flare of the proximal tibia. The POL should be the first structure released when the knee is tight only in extension and not in flexion in a varus TKA.

Another indication for release of the POL occurs when, after release of the posterior fibers of the sMCL, the knee remains tight in extension. The insertion of the POL is released in a subperiosteal fashion from the medial-most point of the tibial cut. This release is directed at a 45° angle in the posterior direction [5].

The SM tendon has a complex attachment to the posteromedial aspect of the tibia, with five described insertion sites. The posterior nature of its blended insertion with the capsule means that the release of the SM tendon affects the extension space more than it does the flexion space.

If the knee remains tight in full extension after the release of the posterior sMCL fibers and the POL, then the release of the SM tendon should be considered. A subperiosteal technique is performed to release the insertion from the posteromedial aspect of the proximal tibia. Although that classically release of the SM tendon was reserved for knees with significant varus deformity or combined varus and flexion contracture deformity, new publications confronts these guidelines. Koh et al. [7] presented a SM release as the second step of their algorithm ((1) release of the deep MCL, (2) release of the SM, (3) release of the sMCL) describing that after realizing the first two steps, only a 6.7% of the patients still required a release of the sMCL to achieve a correct balance, decreasing the risk of instability associated with this procedure (Fig. 9.4).

Other possible releases exist for certain cases but are rarely used in regular practice.