What is Patellofemoral Pain Syndrome (PFPS)?
Patellofemoral pain syndrome (PFPS) is a broad term encompassing all pathologies that cause pain where the patella (kneecap) comes in contact with your femur (thigh bone). This articulation is what is referred to as the patellofemoral joint.¹ PFPS is primarily due to increased patellofemoral joint pressure from poor alignment of the patellar during movement of the knee. Over time this disrupts the surface behind the patella, causing pain.
PFPS is the most common knee pain experienced by the general population, with up to 40% of all knee problems seen in physiotherapy clinics attributed to PFPS. In the general population the prevalence of any symptoms of PFPS annually is 23% among adults and 29% amongst adolescents.² It generally affects females with almost double the prevalence of males and predominantly affects physically active individuals (runners).
WHAT STRUCTURES ARE INVOLVED?
The knee is a hinge joint which mainly allows for knee flexion (bending) and extension (straightening). It consists of the tibiofemoral joint and patellofemoral joint. The tibiofemoral joint involves the articulation of the femoral and tibial condyles and is the weight bearing component of the knee. The patellofemoral joint is where the bottom of the femur and patella combine.³
The patella sits in the trochlea groove of the femur where the patella moves back and forth inside as the knee bends and straightens. Articular cartilage covers the ends of the femur, the trochlear groove and the underside of the patella. This helps your bones glide smoothly against each other as you move your leg. There is also a thin lining of tissue known as the synovium in the knee joint that lubricates the cartilage and assists in the smooth movement of the knee.²⁻³
WHAT CAUSES PFPS?
PFPS is due to the malalignment of the patella as it glides through the trochlea groove. Various factors contribute to the development of PFPS including weakness of specific muscles at the hip and/or knee, muscular tightness around the knee, patella stiffness, poor control and foot posture.¹⁻²⁻³
Overuse and overload of the patellofemoral joint can lead to PFPS with repetitive activities such as running, jumping, squatting as well as going up and down stairs. If the patella has a slight malalignment in the trochlea groove and then loaded with repetitive exercises, an increased pressure is placed on a particular part of the patellofemoral joint which can lead to pain.
Muscular imbalances or biomechanical abnormality can cause a patellar deviation and provoke PFPS. Weakness in the hips, quadriceps and hamstrings can alter the tracking of the patella and increase the risk of PFPS. For example, if the inner quads are weak, the outer quads are exerting a higher force and can cause an overuse of the lateral (outer side) side of the patella due to the patella being pulled laterally.
Flat feet or increased pronation of the feet can impact the alignment of the knee and have been shown to be a predisposing factor for PFPS. Women are also more prone to PFPS due to a great Q angle with wider hips and increased knee valgus.⁴
Direct trauma to the knee or a sudden increase in physical activity can also trigger PFPS symptoms with some increased load on the joint and potentially some inflammation.
WHAT ARE THE SIGNS AND SYMPTOMS?
The presentation of PFPS can vary greatly from person to person however many patients will report the following symptoms;
Pain around the front of the knee often described as an ache
Swelling or inflammation around the knee joint
Pain with prolonged sitting and sitting cross legged
Pain when going up/down hill and going up/down stairs
Pain with running or sports
Pain when coming up from a squat
Grinding or popping sensations with knee movements
Whilst the pain may initially present only with certain activities, like the ones mentioned above, it can progressively worsen to the point where the knee is constantly painful.
TREATMENT
PFPS responds really well to physiotherapy treatment and there is strong evidence to support it.⁵ The physiotherapist will perform a physical assessment to determine the diagnosis of PFPS and the appropriate treatment for your case. The presentation of PFPS varies significantly between individuals and so does treatment. Treatment will first look to reduce the pain caused by the acute response of inflammation and muscle tightness before progressing to correct the underlying cause of pain to prevent it from recurring. Treatment may include a selection of the following; soft tissue massage, patella (kneecap) mobilisation, dry needling, taping techniques, orthotic recommendations and a home strengthening regime for muscles at the hip, knee and potentially foot.⁵⁻⁶
An initial phase of activity modification to reduce pain and alleviate pain to promote healing. Once the pain is controlled, strengthening exercises to improve the strength and control of the muscles around the knee are going to be the essential components of rehabilitation. Recommendations from the literature suggest exercise therapy is used to reduce pain in the short, medium and long terms as well as improve function in the medium and long term.⁶
Once the pain and loading of the knee has improved, to reduce the risk of recurrence a gradual return to training intensity and duration is required. This will ensure the risk of another injury is reduced and allow the load tolerance of the knee to build. Another way to reduce the risk of PFPS is strength training and correct technique.⁵⁻⁶
Strength training and exercises should be focused on combining hip and knee exercises compared to knee exercises alone. In the early stage of strength around PFPS it will be starting with a reduced range of motion, limiting knees over toes (neutral shin angle) and working on strength in the muscle groups around the knee.⁵
The lower body kinetic chain is important to consider as it incorporates the hips down to the toes and therefore, strengthening the whole kinetic chain is vital. Biomechanics can also influence PFPS and by strengthening each component it can lead to adaptations in movements with greater strength. A combination of treatment interventions with exercise therapy, such as orthoses, taping and manual therapy is shown to have the greatest benefits in the treatment of PFPS.⁶
REFERENCES:
1. Kasitinon, D., Li, W.-X., Wang, E. X. S., & Fredericson, M. (2021). Physical Examination and Patellofemoral Pain Syndrome: an Updated Review. Current Reviews in Musculoskeletal Medicine, 14(6), 406–412. https://doi.org/10.1007/s12178-021-09730-7
2. Smith, B. E., Selfe, J., Thacker, D., Hendrick, P., Bateman, M., Moffatt, F., … Logan, P. (2018). Incidence and prevalence of patellofemoral pain: A systematic review and meta-analysis. PLOS ONE, 13(1), e0190892. https://doi.org/10.1371/journal.pone.0190892
3. Crossley, K. M., Stefanik, J. J., Selfe, J., Collins, N. J., Davis, I. S., Powers, C. M., … Callaghan, M. J. (2016). 2016 Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 1: Terminology, definitions, clinical examination, natural history, patellofemoral osteoarthritis and patient-reported outcome measures. British Journal of Sports Medicine, 50(14), 839–843. https://doi.org/10.1136/bjsports-2016-096384
4. Xie, P., István, B., & Liang, M. (2022). The Relationship between Patellofemoral Pain Syndrome and Hip Biomechanics: A Systematic Review with Meta-Analysis. Healthcare. 2022 December 28; volume 11(1): 99. https://doi.org/10.3390/healthcare11010099
5. Alba-Martín, P., Gallego-Izquierdo, T., Plaza-Manzano, G., Romero-Franco, N., Núñez-Nagy, S., & Pecos-Martín, D. (2015). Effectiveness of therapeutic physical exercise in the treatment of patellofemoral pain syndrome: a systematic review. Journal of Physical Therapy Science, 27(7), 2387–2390. https://doi.org/10.1589/jpts.27.2387
6. Collins, N. J., Barton, C. J., van Middelkoop, M., Callaghan, M. J., Rathleff, M. S., Vicenzino, B. T., … Crossley, K. M. (2018). 2018 Consensus statement on exercise therapy and physical interventions (orthoses, taping and manual therapy) to treat patellofemoral pain: recommendations from the 5th International Patellofemoral Pain Research Retreat, Gold Coast, Australia, 2017. British Journal of Sports Medicine, 52(18), 1170–1178. https://doi.org/10.1136/bjsports-2018-099397
