Patellofemoral pain is still baffling clinicians around the world with its causes being hotly debated in the academic community. Some researchers are focussed locally on patellar mal-tracking, whereas others belong to the proximal camp, saying PF pain is primarily a hip problem with the femur collapsing above the knee. Yet others argue PF pain is a distal problem requiring foot and orthotic management.
What the debate demonstrates is that PF pain is a multifactorial problem and there is no one solution to management. Equally, there are individuals with no PF pain who have poor hip control (valgus knee collapse, as it is termed in the literature) and pronated feet. Consider Priscah Jeptoo, the 28 year old silver medalist in the marathon at the London Olympics, who ran for 42 kilometers with internally rotated femurs.
What is missing in this debate is consideration of an individual’s envelope of function –what someone can do without experiencing symptoms. It is all a question of the intensity and frequency of the loading through the knee joint and once an individual’s threshold is reached he/she will become symptomatic.
In everyday activity terms, the load through the knee during walking is 0.05x body weight which increases to 3-4 x body weight during stair ascent and descent and 7- 8x body weight during a squat. If someone has a high threshold of function, poor mechanics, but good muscle control, then he/she will be able to escape the PF curse. However, if the training load is increased or he/she becomes deconditioned, then symptoms will occur. Pain then causes decreased activity in the quadriceps muscle. If it becomes chronic the fear of the pain decreases medial quads activity, which will only exacerbate the mal-tracking of the patella.
As pain inhibits muscle activity, it is essential for the clinician to significantly reduce the patient’s pain, so the patient ‘buys into’ their treatment and will be more compliant with an exercise program.
However, as articular cartilage is aneural, where is the knee pain coming from? The possible sources of PF pain are the synovium, lateral retinaculum, subchondral bone, and the infrapatellar fat pad. The infrapatellar fat pad is one of the most pain sensitive structures in the knee. It stabilises the patella in the extremes of knee motion less than 20degrees and greater than 100 degrees and increases the patellofemoral contact area.
Knee pain has been experimentally induced, by injecting hypertonic saline into the fat pad of asymptomatic individuals. All individuals complained of severe infrapatellar pain, with most also experiencing retropatellar pain and some reporting medial thigh, and even groin pain.
As PF symptoms often recur, one needs to emphasize to a patient that PF pain is not cured, but managed. Patients need to be empowered to manage themselves by doing simple daily strategies that ensure their lower extremity and trunk muscles are working optimally to control their lower limbs in weight-bearing activities so they can enjoy life without PF pain.
For a more in-depth examination of PF pain join us at the 3rd International Patellofemoral Research Retreat in Vancouver, British Columbia. The research retreat is a gathering of scientists who meet every two years to present new research findings and review the science regarding patellofemoral pain.
The retreat will take place over three days (September 18th – 20th, 2013) and include panel discussions and consensus building sessions. We are pleased to confirm two keynote speakers, Professor Paul Hodges (Brisbane, Australia) and Professor Irene Davis (Boston, USA).
In 2013, we are also pleased to announce the 1st International Patellofemoral Pain Clinical Symposium in Vancouver. This one-day symposium is aimed at health and medical practitioners who would like to hear from world experts in the field of patellofemoral pain.
You can also learn more about PF pain as well as the effect of pain and fear of pain on muscle activity by reading Chapter 33, “Anterior knee pain,” and chapter 6, “Pain: why and how does it hurt?” in Clinical Sports Medicine.
Jenny McConnell is a physiotherapist working in private practice in Sydney, Australia and is a fellow of the Australian College of Physiotherapy. Jenny has been involved in research into patellofemoral, shoulder and lumbar spine problems. She recently received an Australia Day Honour when she was awarded a member of the Order of Australia for service to physiotherapy as a practitioner and researcher, particularly through the development of innovative musculoskeletal pain management techniques and treatment.