A 52-year-old woman presents with a 6-month history of progressive right knee pain, worse on stairs and prolonged standing. She has a BMI of 34 kg/m². On examination, there is mild effusion, crepitus on palpation, and pain with patellofemoral compression test. Plain radiographs show joint space narrowing predominantly in the medial compartment with osteophyte formation. MRI reveals cartilage loss and subchondral bone changes. Which ligament is most likely to be secondarily stressed and at risk of degenerative changes due to the underlying pathology?