Matilda suffered a fatal fracture of her tibia and ankle, the doctor had to apply a cast so that she couldn't stand on it or even support herself.
In this clip you can see her using crutches a lot, climbing many stairs, talking about the cast, massaging her toes.
Her leg accidentally falls off a bench which causes a lot of pain, she also tries to exercise at an open gym, then she goes to the shopping center in long, baggy jeans - only a part of her casted foot in a white sock is visible.
Her leg is healing poorly and the doctor decides to amputate it - last scene she walk with stump on crutches.