Background: chondral injuries in the knee are a common source of pain and morbidity. Treatment of symptomatic chondral defects is challenging due to the limited healing capacity of articular cartilage. Microfracture is the most common surgical technique used to treat chondral defects in the knee and utilizes marrow stimulation to generate a fibrocartilage repair. Microfracture has demonstrated good short-term postoperative outcomes. Long-term outcomes following microfracture are variable, with loss of improvement attributed to the poor mechanical qualities of the fibrous repair tissue. Aim of the work: this prospective study with a 12 months follow-up was conducted to determine the efficacy of microfracture in the postoperative follow-up. We prospectively followed up these patients preoperatively and postopertively, clinically and radiologically. The final diagnosis was confirmed during arthroscopy. Patients and Methods: thirty symptomatic patients with articular cartilage defects of the knee were treated with the microfracture technique. Prospective evaluation of patient outcome was performed for a minimum follow-up of twelve months with a combination of validated outcome scores, subjective clinical rating and cartilage-sensitive magnetic resonance imaging. Results: at the time of the latest follow-up, knee function was rated good to excellent for twenty patients (60%), fair for four patients (13%) and poor for eight (26%). A lower body-mass index correlated with higher scores for the activities of daily living, with the worst results for patients with a body-mass index of >30 kg/m2. Significant improvement in the activities of daily living score was more frequent with a preoperative duration of symptoms of less than twelve months (p < 0.05). Magnetic resonance imaging in 15 knees demonstrated good healing in tissue fill of eight patients (54%), moderate fill in four (29%) and poor fill in three patients (17%). The fill grade was correlated with the knee function scores. All knees with good fill demonstrated improved knee function, whereas poor fill grade was associated with limited improvement and decreasing functional scores after twelve months. Conclusions: microfracture healing of articular cartilage lesions in the knee results in significant functional improvement at a minimum follow-up of one year. The best short-term results were observed with good fill grade, low body-mass index and a short duration of preoperative symptoms. A high body-mass index adversely affects short-term outcome, and a poor fill grade was associated with limited short-term durability.