Arthritis is the nation's most common cause of disability. An estimated 50 million U.S. adults (about 1 in 5) report doctor-diagnosed arthritis. Twenty three million U.S. adults of working age (18-64 years) have arthritis; and in this age group arthritis-attributable work limitations affect about 1 in 3 people. An estimated 12% of all patients seeking intervention for symptomatic arthritis have an etiology of previous trauma to the involved joint.

The purpose of this study is to examine these inflammatory compounds in the joint fluid (synovial fluid), the joint lining (synovium), and in blood among subjects with isolated intra-articular fractures.

The hypothesis is that early levels of intra-articular inflammation and markers of joint tissue degeneration following articular fracture in the human knee are predictive of the development of PTA (Post Traumatic Arthritis). Early levels of intra-articular inflammation and markers of joint tissue degeneration identified from human knee joints following articular injury are predictive of the development of PTA in the mouse knee.

Samples of blood, urine and synovial fluid will be taken at the spanning frame surgery and only synovial fluid at the ORIF (Open Reduction Internal Fixation)surgery. Two MRIs (Magnetic Resonance Imaging) will be part of this study at 4 weeks and 18 months.Participants will complete a set of questionnaires(KOOS: Knee Injury and Osteoarthritis Outcome Score) at 4 weeks and 18 months.

40 patients with a closed unilateral articular fracture of the knee requiring operative treatment will be enrolled over an 18 month period. Tissue samples including synovial fluid from the injured and contralateral knee, serum and urine will be collected pre-operatively at the time of framing and ORIF. If patients only need to have one surgery (ORIF) sample will be collected only once. MRI imaging of the injured knee will be obtained after fixation at between week 6 and 8 and at 18 months. Tissue samples will be analyzed for established biomarkers of joint inflammation and degradation. Patients will be followed for 18 months to assess for signs of post-traumatic arthritis. Imaging with plain film and MRI will occur at 18 months. MRI imaging analysis of cartilage thickness and composition changes will be assessed in the injured knees. Assessment of articular cartilage and joint space narrowing and KOOS will be correlated to biomarkers that may be indicative and predictive of joint degeneration and the development of PTA.

Inclusion Criteria:

• Subjects will be adult patients (over 18 years old)
• Patients must present with a unilateral closed intra-articular fracture of the knee.

Exclusion Criteria:

• Pre-existing arthritis in the injured or contra-lateral knee,
• Previous total knee replacement
• Active joint infection
• Pathologic fracture
• Active inflammatory arthritis
• Open fracture of the involved knee
• Contra-lateral knee injury
• HIV infection (if previously known)

Adults that are at least 18 years old and had a unilateral closed intra articular fracture of the knee that requires surgery.