A Prospective Observational Study to Evaluate Long-term Changes in Cartilage Morphology in Subjects Who Previously Received TPX-100 or Placebo in Study TPX-100-1 for Patellar Osteoarthritis Involving Both Knees

No drug intervention. Study to collect 1 additional MRI of each knee treated in either
TPX-100-1 or TPX-100-2.

Inclusion Criteria:

- Subjects who participated in TPX-100-1 and received 4 injections of 200 mg/injection
TPX-100 in one knee, or subjects who participated in TPX-100

- Cruciate and collateral ligament stability as assessed by screening history and
clinical examination

- Stable medial and lateral menisci as assessed by screening history and clinical
examination

- Able to read, understand, sign and date the subject informed consent

Exclusion Criteria:

- Contraindication to MRI, including: metallic fragments, clips or devices in the brain,
eye, or spinal canal; implanted devices that are magnetically programmed; weight > 300
lbs.; moderate or severe claustrophobia; previous intolerance of MRI procedure

- Prior surgery in the knees, excluding procedures for debridement only (no previous
microfracture procedure)

- History of rheumatoid arthritis, psoriatic arthritis, or any other autoimmune or
infectious cause for arthritis

- Last viscosupplementation (e.g. Synvisc® or similar hyaluronic acid product) injected
into either knee < 3 months before enrollment

- Last intra-articular knee injection of corticosteroids < 3 months before enrollment

- Use of any steroids (except inhaled corticosteroids for allergy or respiratory
problems) during the previous month before enrollment

- History of arthroscopy in either knee in the 3 months before enrollment

- History of septic arthritis, gout or pseudo-gout in either knee in the 12 months
before enrollment

- Clinical signs of acute meniscal tear (locking, new acute mechanical symptoms
consistent with meniscal tear)

- Active systemic infection

- Participation in other clinical osteoarthritis drug studies, except for studies
TPX-100-1 and TPX-100-2, within two years prior to enrollment in TPX-100-4.