An Overview of Patellofemoral Stress Syndrome

A Common Cause of Knee Pain

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Patellofemoral stress syndrome, or PFSS for short, is a condition where abnormal rubbing of the kneecap (patella) occurs on the end of the thigh (femur). This a common cause of knee pain and is a common running injury.

Couple running outside
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Location of Pain

If you have pain in the front of your knee, you may be experiencing PFSS. Occasionally the pain is felt around the edges of the kneecap. The pain is typically a sharp burning sensation and is worse with activities like running, jumping, squatting, or climbing stairs. If your condition is severe, walking or rising from a chair may also be painful and may indicate that you have PFSS.

Anatomy of the Patellofemoral Joint

The patellofemoral joint is located in the knee where the patella glides over the end of the femur. There is a small groove at the end of the femur where the patella is seated and held in place by tendons and ligaments. When the patella glides improperly in this groove, pain and inflammation may result, and a diagnosis of PFSS may be suspected.


There are many causes of PFSS. Tightness in muscles around the knee and hip may pull abnormally on the kneecap, pulling it out of optimum position. Weakness in the muscles around the knee and hip may also contribute to the problem. Occasionally, improper foot position while running or walking can cause the knee to turn inward, leading to PFSS. Since many factors that may contribute to PFSS, it is important to check with your healthcare provider and physical therapist to help determine the cause of the problem.


If you are experiencing pain in the front of your knee or around your kneecap, you may have PFSS. A visit to your healthcare provider may be necessary. He or she may choose to take an X-ray to see if arthritis or another condition is causing your pain. A physical therapy evaluation and treatment plan may be necessary to help find the best solution to your problem.

Your physical therapy care should start with a thorough evaluation. This should include a detailed discussion of the history of your problem. Your physical therapist should ask you about when your pain started, how it started, and what activities make your condition better or worse. A detailed history can help your physical therapist decide where the focus of the evaluation should be or if a different problem may be causing your pain. Be sure to wear comfortable clothing to your physical therapy sessions so that your knee is easily accessible.

Your physical therapist may take various measurements to help determine the cause of your problem. He or she may measure the strength of your hip, thigh, or leg muscles. The range of motion of your knees may also be measured. The movement of your kneecap may be measured in various directions and during different activities, like squatting or stair climbing. The flexibility of the muscles of your hip, thigh or leg may also be assessed. Foot and knee position while walking or running may be assessed during a gait evaluation.


Initial treatment for PFSS includes controlling inflammation using the R.I.C.E method for three to five days to help decrease pain and limit swelling around the knee. Ice should be applied to the knee for 15 to 20 minutes several times per day. Be sure to place your ice pack in a towel to avoid tissue damage or frostbite. Avoiding the activity that caused the pain is also a good idea.

After five to seven days of rest and ice application, exercises for PFSS can be started to help improve flexibility and strength around the hip, knee, and ankle. Simple exercises can be performed to ensure that normal tracking of the kneecap is achieved. Be sure to check with your healthcare provider and physical therapist to find out if exercise is appropriate for you and to learn which exercises should be done.

Your physical therapist may also choose to use other physical agents or modalities to help decrease pain and improve mobility. Some common treatments include ultrasound, electrical stimulation, or iontophoresis. Be sure to ask your physical therapist questions about the treatment you are receiving.

After three to four weeks of gentle stretching and strengthening exercises, it may be time to start to prepare to return to normal activity. The pain around your kneecap should be minimal, and you should be able to step up and down stairs without pain.

A simple test to see if your kneecap is tracking properly is the single leg squat test. To perform this, stand on one foot, hold onto something stable, and slowly squat down. If this procedure elicits knee pain, one to two more weeks of gentle exercises may be indicated. If this procedure is pain-free, you should be ready to start training to return to sports.

Advanced strengthening exercises may be necessary to help ensure that your core and lower extremity muscles are providing enough support to the knee. Again, be sure to check with your healthcare provider and physical therapist to help decide which exercises are best for your specific condition.

Your PT can also work with you to change your running gait to keep pressure off your knees in hopes of preventing PFSS. Research indicates that leaning forward slightly while running can reduce stress to your knees to limit pain from runner's knee and PFSS. Your PT can show you how to adjust your running gait for your knees.

A Word From Verywell

Most episodes of PFSS get significantly better in about six to eight weeks. If your specific condition is more severe, it may take a bit longer to achieve pain-free function. If your symptoms persist after eight weeks, you should consult with your healthcare provider to see if more invasive treatments, like injections or surgery, would help you.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. OrthoInfo. Patellofemoral pain syndrome.

  2. Lobo P, Barbosa IA, Borges JHS, Tobias RF, Boitrago MVDS, Oliveira MP. Clinical Muscular Evaluation in Patellofemoral Pain Syndrome. Acta Ortop Bras. 2018;26(2):91-93. doi:10.1590/1413-785220182602187215

  3. Peters JS, Tyson NL. Proximal exercises are effective in treating patellofemoral pain syndrome: a systematic review. Int J Sports Phys Ther. 2013;8(5):689-700.

  4. Alba-martín P, Gallego-izquierdo T, Plaza-manzano G, Romero-franco N, Núñez-nagy S, Pecos-martín D. Effectiveness of therapeutic physical exercise in the treatment of patellofemoral pain syndrome: a systematic review. J Phys Ther Sci. 2015;27(7):2387-90. doi:10.1589/jpts.27.2387

Additional Reading
  • Teng, H, Powers, C. Influence of trunk posture on lower extremity energetics during running. Med Sci Posrt and Exer. 47(3) March 2015. 625-630.

  • Hertling, D. (2006). Management of common musculoskeletal disorders. (4th ed.). Philadelphia: Lippincott Williams & Wilkins.

By Brett Sears, PT
Brett Sears, PT, MDT, is a physical therapist with over 20 years of experience in orthopedic and hospital-based therapy.