LY517717 (a capsule given by mouth) is a blood thinner that may prevent blood clots from forming in the legs and may prevent those blood clots from traveling to the lungs. Leg and lung blood clots occur commonly after patients have surgery to replace a hip or knee joint. These clots often occur while patients are in bed in the hospital after hip or knee joint surgery. The purpose of this study is to test if different dose strengths (amount of drug in the capsules) of LY517717 can prevent blood clots from forming and to determine if LY517717 is safe. This study will compare LY517717 to enoxaparin, another blood thinner. Enoxaparin is one of the standard medications given after hip or knee joint surgery.

Inclusion Criteria:

• Are scheduled for total knee or hip replacement surgery (only one side, first time joint replacement)
• Are at least 18 years of age and no more than 75 years of age.
• Have a body weight more than 50 kg and less than 120 kg.
• Sign an approved Eli Lilly and Company informed consent document.

Exclusion Criteria:

• Have had hip or knee replacement surgery in the non-surgical leg or any surgical procedure in the surgical leg within 6 months prior to enrollment.
• Other surgeries (brain, spinal cord, eye within 12 months; chest or abdominal surgery within 1 month).
• Have taken drugs that might increase possibility of bleeding.
• Other risk factors for bleeding (bleeding disorders, abnormal results on blood tests, ulcers)
• Increased risk for blood clots.