311 patients with an irreparable injury of the medial meniscus or a previous partial medial meniscectomy were divided into 2 study arms: acute arm with no prior surgery on the involved meniscus or the chronic arm with 1, 2 or 3 prior meniscal surgeries. Patients were randomized either to receive the collagen meniscus implant or to be treated with a partial meniscectomy only. Clinical follow-up examinations were performed for 2 years postoperatively, and patients were to complete validated questionnaires 7 years postoperatively. Patients allocated to receive the collagen meniscus implant also underwent 1-year second-look arthroscopy to assess tissue growth and quality. Results indicated that the collagen meniscus implant was found to support new tissue ingrowth, which was stable, safe, and biomechanically competent and improved meniscal function, as evident by the clinical outcomes in patients with a chronic meniscal injury.