Clinical Trial for the Regeneration of Cartilage Lesions in the Knee

Inclusion Criteria: * Patient is ≥18 and ≤65 years old at time of screening. * Patient has a localized articular cartilage defect of the femoral condyle and/or the trochlea of the knee. 2 localized cartilage defects are accepted if the total defect size is ≤ 8 cm2, both cartilage defects are located at the femoral condyle and/or the trochlea and both cartilage defects are to be treated with N-CAM or N-TEC. * Patient has a defect of grade 3 or 4 according to the ICRS classification. * Patient has a defect size ≥2 and ≤8 cm2 as assessed by MRI/arthroscopy. * Patient has an intact (≤ICRS Grade 2 ) articulating joint surface (no "kissing lesions"). * Patient has an intact meniscus (maximum 1/2-resection). * Patient has a stable knee joint or sufficiently reconstructed ligaments. If not, ligament repair has to be done during the operation or within 6 weeks of the planned cartilage treatment. * Patient has a maximum baseline score of 75/100 in the KOOS subjective knee evaluation. * Patient is willing and able to give written informed consent to participate in the study and to comply with all study requirements, including attending all follow-up visits and assessments and to complete postoperative rehabilitation regimen. Exclusion Criteria: * Patient is the investigator or any sub-investigator, research assistant, pharmacist, study coordinator, other staff or relative thereof directly involved in the conduct of the protocol or in a dependency or employment with the sponsor. * Patient is unable to understand the patient information * Patient is unable to undergo magnetic resonance imaging (MRI) or is sensitive to gadolinium * Patient has had prior surgical treatment of the target knee within 12 months using mosaicplasty and/or microfracture (Note: prior diagnostic arthroscopy with debridement and lavage are acceptable within 12 months). Anterior cruciate ligament repair is accepted, if the target knee is stable or a primary Anterior cruciate ligament (ACL) reconstruction is performed within 6 weeks of the planned cartilage treatment. * Patient has a relevant meniscus tear. Partial meniscal removal allowed, if not exceeding 1/2. Meniscus suture is not allowed in parallel, but if successful, cartilage treatment might be added 12 months later. * Patient has radiologically apparent degenerative joint disease in the target knee as determined by Kellgren and Lawrence grade \>2. * Patient has chronic inflammatory arthritis, and/or infectious arthritis. * Patient has an unstable knee joint or insufficiently reconstructed ligaments. If ligament repair is necessary, the repair has to be performed during the operation or within 6 weeks of the planned cartilage treatment. * Patient has malalignment (no valgus- or varus-deformity) in the target knee ≥ 5°. In suspected cases, the mechanical axis must be established radiographically through complete leg imaging during standing and in a.p. or rather p.a. projection. If alignment surgery is necessary, surgery has to be performed within 6 weeks of the planned cartilage treatment. * Patient has an osteochondral defect (defined as bony substance defect of \>3mm depth). Bone marrow edema is allowed. * Patient has relevant bilateral lower limb pain. * Patient has a known systemic connective tissue disease. * Patient has a known autoimmune disease. * Patient has a known immunological suppressive disorder or is taking immunosuppressives. * Patient is currently systemically or intra-articularly taking steroids and/or has used steroids within the 30 days prior to the planned treatment. * The patient has a known history of HIV/AIDS. (Protection of staff) * The patient has a known history of Treponema pallidum (syphilis). (Protection of staff) * The patient has an active hepatitis B or C infection with verified antigens. Patients with a cured hepatitis B or C infection and/or verified antibodies are not excluded. (Protection of staff) * The patient has at the site of surgery an active systemic or local microbial infection, eczematization or inflammable skin alterations (including protozoosis: Babesiosis, Trypanosomiasis (e.g. Chagas-Disease), Leishmaniasis, persistent bacterial infections, such as Brucellosis, spotted and typhus fever, other Rickettsiosis, Leprosy, Recurrent Fever, Melioidosis or Tularaemia). * Patient has a known history of cancer. * Patient has a known history of primary hyperparathyroidism, hyperthyroidism, reduced kidney function, chronic renal failure or prior pathological fractures, independent of the genesis. * Patient has any degenerative muscular or neurological condition that would interfere with evaluation of outcome measures including but not limited to Parkinson's disease, amyotrophic lateral sclerosis (ALS), or multiple sclerosis (MS). * Patient has a body mass index (BMI) \>35 kg/m2. * Patient is pregnant, lactating or anticipates becoming pregnant within 24 months after surgery. * Patient is currently participating, or has participated in any other clinical study within 3 months prior to the screening visit. * Patient has known current or recent history of illicit drug or alcohol abuse or dependence defined as the continued use of alcohol or drugs despite the development of social, legal or health problems. * Patient has psychiatric or cognitive impairment that, in the opinion of the investigator, would interfere with the patient's ability to comply with the study requirements, e.g., Alzheimer's disease. * Patient has any other condition, which, in the opinion of the investigator, would make the patient unsuitable for the study. * Patient is unable to tolerate local anesthesia * Any known allergies, especially for porcine collagen, penicillin or streptomycin * Patient is unwilling and/or unable to give written informed consent to participate in the study and to comply with all study requirements, including attending all follow-up visits and assessments and to complete postoperative rehabilitation regimen. Intraoperative Exclusion Criteria: * Patient has a total defect size \<2 or defect size extends graft size and could therefore not be treated in total. * Patient has \>2 independent cartilage lesions * Patient has symptomatic full-thickness (ICRS Grade 3 or 4) of patella or tibial plateau.