The study was designed by the principal investigator, Dr. Andrea Veljkovic, and the St. Paul's Hospital Foot and Ankle Research Group, who will conduct the study. The study is being funded by Arthrex, Inc., the manufacturer of the Health Canada approved BioCartilage® Micronized Cartilage Matrix.

The purpose of this study is to assess whether adding BioCartilage® to microfracture treatment of osteochondral defects of the talus improves osteochondral healing as well as improving pain and function.

Efficacy will be assessed primarily by outcomes scores as measure by the Ankle Osteoarthritis Scale (AOS) at the baseline and at multiple post-op followup visits. Additional outcomes scores will also be administered to compare general health and foot function between the two groups at baseline and at multiple post-op followup visits. X-rays and MRI will be used to assess the osteochondral healing rate.

Inclusion Criteria:

1. The subject has signed the REB approved informed consent form (ICF) specific to this study prior to enrollment.
2. The subject has an isolated OCD with minimum dimensions of 0.07 cm2 (0.3 cm in diameter) and maximum dimensions of 2.25 cm2 as confirmed by a pre-op MRI.
3. The subject is independent, ambulatory, and can comply with all post-operative evaluations and visits.
4. The subject is at least nineteen (19) years of age and considered to be skeletally mature.
5. The subject has a combined bone and cartilage defect as determined by an MRI.
6. The patient has a stable ankle joint on history and has similar ligament stability with the opposite ankle.
7. The subject has less than 15 degrees of hindfoot valgus and 5 degrees of hindfoot varus.
8. The subject has a chronic defect not secondary to acute trauma within the last 6 months.
9. The patient (if having suffered a fracture) has no residual deformity of the tibia, fibula or syndesmosis.
10. The subject has a BMI of ≤ 40 kg/m².
11. The subject has exhausted non-operative treatment.
12. The subject has symptoms for less than a year.
13. Lesions on the subject must be contained.

Exclusion Criteria:

1. The subject has over 15 degrees of hindfoot valgus or 5 degrees of hindfoot varus.
2. The subject has an isolated OCD with dimensions greater than 2.0 cm2 on an MRI assessment.
3. The subject has an allergy to yeast-derived products.
4. The subject has implanted metallic devices (cardiac pacemakers, insulin pumps, and nerve stimulators), medically implanted clips, or other electronically, magnetically or mechanically activated implants that would contraindicate an MRI scan of the foot.
5. The subject has claustrophobia that would inhibit their ability to undergo an MRI scan of the foot.
6. The subject has tested positive or has been treated for a malignancy in the past, is suspected of having a malignancy, or is currently undergoing radiation or chemotherapy treatment for a malignancy anywhere in the body, whether adjacent to or distant from the proposed BioCartilage® site.
7. The subject is physically or mentally compromised (e.g., currently being treated for a psychiatric disorder, senile dementia, Alzheimer's disease, etc.), to the extent that the investigator judges the subject to be unable or unlikely to remain compliant to follow-up.
8. The subject is a prisoner, or is known or suspected to be transient.
9. The subject has documented evidence of a history (e.g. liver testing) of drug/alcohol abuse within the 12 months prior to screening for study entry.
10. The subject is pregnant or able to become pregnant but not practicing a medically-accepted form of birth control, and/or intending to become pregnant during this study period.
11. The subject currently has an acute infection in the area surrounding the surgical site.
12. The subject has a history of anaphylaxis or of multiple non-environmental allergies that may precipitate an anaphylactic reaction.
13. The subject's condition is bilateral and surgery is scheduled or to be scheduled over the course of this trial for both feet.
14. The subject requires a concomitant osteotomy of the tibia, fibula, or calcaneus for hindfoot deformity.
15. The subject requires a concomitant hindfoot fusion or has had a hindfoot fusion for hindfoot arthritis or deformity.
16. The subject is undergoing any concomitant surgery that may invalidate the outcome scores such as forefoot surgery or fusions, tendon transfers or ligament reconstructions. Heel cord lengthening is permitted.
17. The subject has an OCD of the tibia in isolation or in combination with the talar lesion
18. The subject is addicted to nicotine and on nicotine containing medication such as gum or a patch; or using nicotine containing substances such as cigarettes, cigars, pipe smoking or chewing tobacco.
19. The subject abuses cocaine or cocaine derivative drugs.
20. The subject has a known hypersensitivity to aprotinin.
21. The subject has diabetes with an HBA1c> 7.5.
22. The subject is unable to give informed consent.
23. The subject is unable to comply with follow-up.
24. The subject is unable to communicate with the research team.

This study will be single-blinded. Group I and II subjects will be blinded as to whether they have received BioCartilage® in addition to Microfracture or Microfracture alone, as per standard of care. Investigators will be aware of the assigned treatment on the patients. Subjects will be aware of their assigned treatment after their surgery.