Currently a standard tourniquet pressure is used for orthopedic surgeries. High tourniquet pressure had been associated with adverse side effects such as ischemia, muscle weakness, and post operative pain. Limb Occlusion Pressure, LOP, is based off the patient's systolic blood pressure plus a safety margin and is typically much lower than standard tourniquet pressure. The aim of this study is to determine if using LOP during orthopedic surgeries decreases post-operative pain and opioid consumption and improves patient's outcomes.

The study will start for each subject in the clinic setting during a standard pre-operative office visit. Consent for the study will be obtained after explaining all aspects of the study. The subjects will be randomly separated into two groups. Half of the subjects will have their procedure performed under standard tourniquet pressure, and the other half of the subjects will have their procedure performed with a distal photoplenthysmography probe that will calculate Limb Occlusion Pressure and inflate the tourniquet to the calculated Limb Occlusion Pressure. The subject will undergo their scheduled procedure in the operating room. The subject will also keep a daily pain and opioid consumption diary at home for two weeks after the surgery. The subject will complete patient outcome questionnaires before the surgery, two weeks after the operation, and 8 weeks after the operation to assess patient outcomes. The subject can complete the questionnaires at home, but if they do not, they will have the option to fill the out during their clinic visits. The patient's pre and post OP questionaries' will be the indicators for patient outcomes. All of the standardized questionnaires give calculated scores based off the patients' responses. As the subject improves their score will increase.The research team can compare change in score between the two groups and change with in groups to access patient outcomes.

To maintain the double blind nature of the study, the tourniquet will be placed, inflated, and draped over before the surgeon enters the operating room. Someone else on the research team, one of the coordinators or one of the residents will record the patients' systolic blood pressure and cuff pressure of the tourniquet before the attending enters the OR. This way the surgeon is still blind to the cuff pressure technique used, LOP or STP, when they rate the quality of the bloodless field after the surgery using a VAS scale.

All of these documents are attached on the summary page under additional documents on the Psycho-Physiological Testing page under number 1. List all the measures/instruments that will be used for this study. The VAS pain and opioid consumption diary is titled LOP pain diary cover page and LOP pain diary. The questionnaires that will be used are DASH, IKDC Subject Knee Evaluation Form, KOOS Junior, KOOS Lysholm, Marx, Michigan Hand Outcomes, Patient Rated Wrist Evaluation, Promis Bank v 1.2 Physical Function, PROMIS SF v 1.1 Global Health, and Tegner Activity Level Scale.

Inclusion Criteria:

• The research team will test the central hypothesis that LOP tourniquets will decrease pain and opioid use and improve patients outcomes on healthy adults (above the age of 18) undergoing either open carpal tunnel release, open reduction internal fixation distal radius fracture, cubital tunnel release, trigger finger release, thumb CMC arthroplasty, anterior cruciate ligament reconstruction, or total knee replacements

Exclusion Criteria:

1. Prescription pain medications for chronic conditions (> 6 weeks)
2. Patients who cannot use a tourniquet:( ex. Certain patients with fistulas or PVD, certain patient with Peripheral Vascular Disease)
3. Prior trauma or surgery to the observed limb.
4. Hypotension or hypertension that prevents accurate distal photoplenthysmography probe reading.

Neither the subject nor the operating surgeon know the which group the subject is randomized to.