Available online 14 March 2022, 150915

The medial collateral (MCL) and fibular collateral (FCL) ligaments are the primary frontal plane stabilizers in the knee joint. Extreme varus, valgus, or rotational moments about the knee may cause the failure of these ligaments and contribute to persistent knee instability and functional deficits that may not respond to rehabilitation alone. Surgical intervention may be warranted when a complete disruption occurs to address resultant instability. Due to lower incidences of surgery to address MCL and FCL injuries, by comparison to anterior cruciate ligament reconstruction (ACLR), fewer high-quality studies exist addressing postoperative rehabilitation guidelines for the collateral ligaments. Additionally, little is known on performance-based outcomes and return to sport within this population, especially within the postoperative population. Standardized postoperative protocols for this population currently do not exist in the literature. Therefore, basic science on collateral ligament anatomy and biomechanics provides the foundation for postoperative rehabilitation, including precautions and the continuum of care to return a patient to sport. The objective of this text is to define the rationale for postoperative precautions, provide a template for phased rehabilitation strategies, and describe physical performance testing protocols to guide decisions on care progression and return to activity/sport following surgery to address medial and lateral knee instability.

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