Observational StudyThe HYALEX Pivotal Study

Inclusion Criteria (Phase 1):

1. 22-70 years.
2. Body Mass Index (BMI) ≤ 40.
3. Up to two treatable joint surface lesion, ICRS Grade 3 or 4, located on the medial and/or lateral femoral condyle.
4. Up to 2 implants (one implant per condyle) to treat up to 2 individual symptomatic lesions with a total summative area up to 4.52cm2 / condyle.
5. Knee Injury and Osteoarthritis Outcome Score (KOOS) pain subscale score between 20 and 65.
6. Ligamentously stable knee.
7. Failure of non-operative treatment (e.g., physical therapy, physician-directed at home exercise program, intra-articular injections, bracing) for at least 4 months prior to consideration for participation in the study.

Exclusion Criteria:

HYALEX Implant, Surgical Technique, and Lesion Site Exclusions:

1. Known allergy to polyurethanes, bone cement, acrylic, or titanium.
2. Lack of 2mm of cartilage (ICRS Grade 0 to 2) and 2mm of vital bone wall on all sides of the implant site.
3. Osteochondral defect affecting subchondral bone more than 11mm in depth from adjacent non-defect articular surface.
4. Bipolar cartilage lesions involving patellar or tibial lesions ICRS Grade 3 - 4 opposite the lesion intended for treatment.
5. Insufficient bone stock or bone density determined intra-operatively preventing implant press fit.

Patient Orthopaedic Health Exclusions:

1. Kellgren and Lawrence (KL) grade 3 or 4 on standing radiographs.
2. Hip-knee-ankle (HKA) angle of greater than +/- 8 degrees (varus or valgus malalignment > 8 degrees) on standing X-ray.
3. Lack of normally functioning contralateral knee that restricts activity.
4. Recent Osteochondritis Dissecans within 1 year.
5. Diagnosis of a concomitant knee injury which the investigator believes may interfere with study participation or confound effectiveness assessment.
6. Untreated ACL and/or PCL deficiency or complex ligamentous instability of the study knee according to IKDC Grade C (abnormal) or D (severely abnormal).

Previous Surgery and Intervention Exclusions:

1. Previous surgical cartilage treatment in the index knee within the last 6 months
2. Previous intra-articular injections, including HA and steroids, within the last 3 months prior to the date of surgery.

Patient Overall Health and Health History Exclusions:

1. Any known history of inflammatory arthropathy or untreated or uncontrolled crystal-deposition arthropathy.
2. Current cigarette smoker or user of other nicotine products.
3. Known Type 1 or Type 2 insulin-dependent diabetes mellitus.
4. Currently undergoing immunosuppressive therapy or long-term steroid use (corticosteroid, excluding inhalers) or within 3 months prior to surgery.