Blood flow restrictive (BFR) therapy following MPFL or ACL reconstruction rehabilitation.

Specific Aim 1: Test whether maintaining BFR cuff inflation or deflating between exercises results in greater quadriceps strength and functional outcomes after MPFL or ACL reconstruction.

Hypothesis 1: Subjects in the deflate BFR protocol group will have significantly greater quadriceps strength, symmetric leg symmetry index on a battery of functional tests and PROs as compared to the non-deflate group.

Specific Aim 2: Compare whether maintaining BFR cuff inflation or deflating between exercises results in reduced pain, improved exercise tolerance, and patient-reports outcomes (PRO) after MPFL or ACL reconstruction.

Hypothesis 2: Subjects in the deflated BFR protocol group will report significantly less pain and greater exercise tolerance during exercise with significantly improved knee related PRO scores.

Subjects will be aged 13-40 male or female patient following MPFL or ACL reconstruction.

Baseline Assessment at PT Evaluation will included knee AROM and AAROM Heel slide with strap, Knee edema measured in cm difference Involved to Non-involved at supra and mid patellar levels, subjects ability to SLR Yes/No in brace, Patient reported outcome measure (PRO's) to include LEFS, Brief Resiliency scale, MPFL - Norwich Patellar instability, ACL 2000 IKDC Subjective Knee Evaluation Form questionnaires. Pain assessment to include current, minimal and maximal pain levels past 24 hours.

Patient are randomized into 1 of 2 groups: Group 1 will deflate between BFR exercises, Group 2 will not deflate between BFR exercises. Both groups will receive the same standard care same during their first 2 weeks of post-op rehabilitation. BFR will be added to their rehabilitation care starting at week 3 for 2x/week x 10. There are 4 core BFR exercises that will be progressed every 2 weeks.

Final Assessment- Strength and Functional Testing at 24th visit or 12 weeks post-op (if missed appointments) to include bilateral Knee AROM and edema assessments, PRO's: LEFS, Brief Resiliency scale, MPFL Norwich Patellar instability, ACL 2000 IKDC Subjective Knee Evaluation Form, Functional assessment to include for involved adn uninvolved leg: Isometric Quad strength measurement at 90 degrees of knee flexion, Isometric Hip Abduction strength measurement, Y balance maximum anterior reach, Max reps 6" Forward step-down, max core strength assessments, and ability in-line jog.

Inclusion Criteria:

Post operative Medial Patellar Femoral Ligament or Anterior Cruciate Ligament Reconstruction.

Exclusion Criteria:

• Had any other previous surgeries or conditions that might affect your gait prior to injury and 1 year removed from a prior ACL or MPFL reconstruction.
• Have any current lower extremity condition other than MPFL or ACL reconstruction which might affect your gait
• Have a diminished capacity to provide informed consent
• Are diabetic or have uncontrolled hypertension
• Have recent inflammation, bleeding disorders, active bleeding or infection within the lower limbs.
• You are taking warfarin/Coumadin, clopidogrel/Plavix, Rivaroxaban/Xarelto, Dabigatran/Pradaxa, apixaban/Eliquis, deoxidant/Savaysa, betrixaban, or any other anti-coagulants that may cause excess bleeding.
• Have any implanted medical device
• Have a history of deep vein thrombosis, vascular graft, varicose veins, and/or sickle cell anemia
• Are or suspect you are Pregnant
• You are not be able to attend regular physical therapy or study visits