Chronic Patellofemoral Pain Syndrome (PFPS) or Chondromalacia Patellae: This condition is likely given the patient's history of knee pain since high school, particularly with activities that increase stress on the knee, such as catching and running. The crunching or cracking sound (crepitus) and swelling at the end of the day, along with the knee giving out, are common symptoms of PFPS. The ineffectiveness of previous physical therapy (PT) sessions and the use of various knee braces and KT tape without significant relief also point towards a chronic condition like PFPS.

Osteoarthritis (OA): Although the patient is relatively young, the history of a knee injury (being knocked out of place) and chronic stress from sports could contribute to early-onset OA. Symptoms like pain with activity, swelling, and crepitus are consistent with OA.
Meniscal Tear: Given the patient's history of a significant knee injury (the knee being knocked out of place), a meniscal tear is possible. Symptoms such as pain with activity, swelling, and the sensation of the knee giving out could be indicative of a meniscal tear.
Ligamentous Injury: The history of the knee being knocked out of place suggests a possible ligamentous injury, which could contribute to chronic instability and pain.

Septic Arthritis: Although less likely given the chronic nature of the symptoms, septic arthritis is a medical emergency that requires prompt diagnosis and treatment. Any signs of infection, such as fever, significant swelling, or redness, would necessitate immediate investigation.
Osteonecrosis: This condition, also known as avascular necrosis, could be a consequence of previous trauma or chronic stress on the knee. It's crucial to consider, especially if the patient has experienced significant pain or if previous treatments have been ineffective.
Tumor: Although rare, a tumor (benign or malignant) could cause chronic pain and should be considered, especially if there's a significant change in symptoms or if previous diagnostic tests have not been comprehensive.

Plica Syndrome: This condition involves inflammation of the synovial folds within the knee joint, which can cause pain and snapping sensations. It's less common but could be considered if other diagnoses are ruled out.
Osgood-Schlatter Disease: Typically seen in adolescents, this condition involves inflammation of the patellar tendon at its insertion on the tibia. Although the patient is older, if she experienced symptoms during her adolescent years that have persisted, this could be a rare consideration.