Knee osteoarthritis (OA) is often associated with varus malalignment, leading to increased loading of the medial compartment and accelerating joint degeneration. Accurate estimation of knee contact forces (KCF) and pressures is essential for understanding disease progression and treatment planning. However, conventional musculoskeletal models predict joint loads using simplified joint representations and neglect ligament and cartilage contributions. This thesis aimed to estimate KCF and pressures in a patient with medial knee OA and varus malalignment using a subject-specific musculoskeletal model incorporating ligament and cartilage contact mechanics. Additionally, results were compared with a previously-developed conventional model based on fixed contact points to evaluate the influence of contact mechanics on load distribution and contact location.