Patellofemoral pain (PFP) is a common running-related injury that is often referred to as runner's knee. The condition typically presents with pain in the front of the knee that is located around or behind the knee cap. This injury occurs twice as frequently in females and is often associated with weakness of the muscles of the thigh and hip, as well as altered running form. Heavy-weight strength training is needed in order to improve muscle weakness; however, this puts a significant amount of load on the knee joint and it is difficult for individuals with PFP to train at this level without experiencing increased pain and joint discomfort. Blood flow restriction training (BFRT) is a promising alternative method to safely improve muscle weakness while reducing knee joint loading. With BFRT, a pressurized band is applied to the thigh in order to partially restrict blood flow as a patient exercises in order to decrease the amount of oxygen delivered to the muscle. Lack of oxygen to the muscle combined with strength training creates an environment within the muscle that results in the ability of low-weight strength training to provide the same results as heavy-weight strength training.

This study will evaluate how low-weight strength training with and without BFRT affects thigh and hip strength, and consequently pain, function, running ability, and running form in female runners with PFP. The hypothesis is that 10 weeks of low-weight strength training with BFRT will lead to greater thigh and hip strength, reduced pain, improved knee function, improved running ability, and improved running form compared to low-weight strength training without BFRT. The expected results will have a significant impact within the running community by providing a safe and effective treatment that increases strength and improves running form while reducing pain and joint loading. This will also have an impact on the larger field of sports medicine by providing an alternative method to improve strength, as well as improve function when heavy-weight strength training is not well tolerated or unsafe due to injury.

Inclusion Criteria:

• Pain around (peripatellar) or behind (retropatellar) the patella, which is aggravated by running and at least one other activity that loads the patellofemoral joint during weight bearing on a flexed knee such as kneeling, squatting, stair ambulation, and jumping/hopping
• Insidious onset of symptoms unrelated to trauma
• Pain present for at least 2 months
• Pain rating of at least 3/10 on the visual analog scale during running
• Report running at least 10 miles per week currently or just prior to onset of injury
• Score a maximum of 85% on either the Knee Outcome Survey Activities of Daily Living Scale or Sports Activity Scale (KOS-ADL or KOS-SAS)

Exclusion Criteria:

• Knee pain resulting from acute trauma
• Concurrent ligamentous instability, meniscus pathology, patellar or iliotibial band tendinopathy
• History of patellar dislocations or instability, or previous reconstructive surgery to the knee
• Other lower extremity or lower back injury within the past 6 months