patellofemoral pain syndrome review cover

Review of Patellofemoral Pain Syndrome

Patellofemoral pain syndrome (PFPS) is a spectrum of anterior knee pain originating from the patellofemoral joint. Generally speaking, the term “patellofemoral pain” is not well defined and the cause(s) of pain are complex and multifactorial. The term covers most causes of anterior knee pain and is often referred to as “Runner’s Knee”. This article will attempt to succinctly review PFPS. 

Illustration of the general distribution of patellofemoral pain.

PFPS is the most common cause of knee pain in adults under the age of 50.[1]Davis IS, Powers CM. Patellofemoral pain syndrome: proximal, distal, and local factors, an international retreat, April 30–May 2, 2009, Fells Point, Baltimore, MD. J Orthop Sports Phys Ther … Continue reading It is 2 to 10 times more common in women than men. It is also the most common cause of knee pain in pediatric and adolescent patients. The prevalence is reported to be between 23% and 43% depending on the population being studied. Among naval academy recruits, the incidence is 22 per 1000 person years.[2]Crossley KM, van Middelkoop M, Callaghan MJ, et al. Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 2: recommended physical … Continue reading

The etiology of PFPS is multifactorial and frankly not well understood. Multiple contributing factors have been identified and, in most cases, no single cause can be attributed to the symptoms. Contributing factors that must be considered include (a) patellar maltracking or malalignment, (b) weakness of the vastus medialis, (c) Quadriceps dysfunction, (d) Dynamic valgus and Q angle, (e) Weakness in hip stability and abductor strength, (f) Disorders of the foot, (g) hamstring imbalance and tightness, (h) Iliotibial band tightness, (i) psychological factors, (j) overload or overtraining of the joint among many considerations. The etiology can include overuse (tendinitis and tendinosis), patellar instability, osteochondral lesions and trauma.

Associated/ related conditions include: 


    • Chondromalacia Patellae
    • Osteochondral Defect Knee
    • Patellofemoral Osteoarthritis
    • Extensor Tendinopathy
    • Patellar Instability
    • Plica Syndrome
    • Infrapatellar Fat Pad Impingement
Risk factors can be broken down into modifiable and non modifiable. Non modifiable risk factors include include female gender and poor footwear/ running surface. Modifiable risk factors are extensive. Select modifiable risk factors include running and jumping sports, training errors, weakness in knee extensors, hip abductors and external rotators. Biomechanical and anatomic risk factors include a large Q angle, patellar hypermobility, limb length discrepancy, and a positive J sign.
Demonstration of the moving patella apprehension test.[3]Halabchi, Farzin, et al. “Patellofemoral pain in athletes: clinical perspectives.” Open access journal of sports medicine (2017): 189-203.

History is usually insidious and the pain is universally anterior. Typically the pain is around the patella although the patient may have trouble localizing the pain. Pain is almost always worse after prolonged sitting, car rides, kneeling, squats and stairs. Patients can report clicking, popping and snapping. Pain is often bilaterally.

On physical exam, an effusion is typically absent. The patient may have a positive patellar J sign, indicated by laterally tracking patella which shifts medially as the knee is flexed, forming a “J”. Carefully evaluate muscle bulk, which emphasis on the VMO and compare to the contralateral limb. Crepitus may be present. Tenderness along the patella is common. Carefully evaluate the back and hip for referred pain.

The normal radiograph (b, grade 0) is contrasted to grade1, grade2, and grade 3 abnormal radiographic features (a) on the skyline view of the patellofemoral joint. Abbreviations. LJSN: lateral joint space narrowing; MJSN: medial joint space narrowing; LPOST: lateral patellofemoral osteophyte; MPOST: medial patellofemoral osteophyte.[4]Qiu, Yudian, et al. “Imaging features in incident radiographic patellofemoral osteoarthritis: the Beijing Shunyi osteoarthritis (BJS) study.” BMC Musculoskeletal Disorders 20 (2019): 1-6.
(a) Patella alta. Sagittal T2 Fat Sat image in a 20 year old female complaining of knee pain with an Insal-Salvati ratio of 1.7. (b) Patella baja. Sagittal T2 Fat Sat image in a 32 year old male complaining of knee pain with an Insal-Salvati ratio of 0.7.[5]Fahmy, Hadeer Safwat, et al. “Role of MRI in assessment of patello-femoral derangement in patients with anterior knee pain.” The Egyptian Journal of Radiology and Nuclear Medicine 47.4 … Continue reading

Imaging is not required to make the diagnosis, which is primarily clinical. Initial radiographs may be normal. Potential findings include patellofemoral arthritis, osteochondral defect, patellar tilt, and bipartite patella. Ultrasound can be used to evaluate the extensor mechanism and can quantify the size of the quadriceps tendon, patellar tendon and vastus medialis to compare to the contralateral limb. MRI can show trochlear malalignment, trochlear dysplasia, patellar tilt, osteochondral lesions. Finally, CT can be used to evaluate the patellofemoral bones and measure the tibial tubercle-trochlear groove distance.

Management is non surgical in most cases. The general objective is to reduce compressive forces on the patellofemoral joint and alter the distribution of stress forces on the patella. First line therapy is relative rest and activity modification combined with physical therapy. Physical therapy will emphasize quadriceps strengthening, hip adductors, and external rotators all of which have been shown to reduce pain symptoms.[6]Harvie D, O’Leary T, Kumar S (2011) A systematic review of randomized controlled trials on exercise parameters in the treatment of patellofemoral pain: what works? J Multidiscip Healthc 4:383–392 The use of blood flow restriction training has been shown to provide benefit in patients undergoing physical therapy, again with an emphasis on the quadriceps/ VMO.
Illustration of some basic rehab movements for patellofemoral pain

Pharmacotherapy can include NSAIDS, topical NSAIDS and vitamin D. Bracing and taping have shown significant benefit with the primary objective of modifying lateral patellar tracking and emphasizing medialization. So called “McConnel taping” is commonly accepted among athletes as a way to reduce pain and improve function.[7]Warden SJ, Hinman RS, Watson MA Jr, Avin KG, Bialocerkowski AE, Crossley KM (2008) Patellar taping and bracing for the treatment of chronic knee pain: a systematic review and metaanalysis. Arthr … Continue reading Patella braces offer the same value but can be slightly more cumbersome. In patients with foot and ankle dysfunction, foot orthosis have been shown to reduce patellofemoral pain.[8]Collins NCrossley KMBeller EDarnell RMcPoil TVicenzino B. Foot orthoses and physiotherapy in the treatment of patellofemoral pain syndrome: randomised clinical trial. Br J Sports Med. … Continue reading

The benefit of many modalities for PFPS remains unknown. This includes therapeutic ultrasound, acupuncture, TENS, massage therapy and dry needling among others. In most patients, the evidence is lacking to support corticosteroid injections. One study looked at injecting botulinum toxin in the vastus lateralis which showed promise.[9]Kesary Y, Singh V, Frenkel-Rutenberg T, et al. Botulinum toxin injections as salvage therapy is beneficial for management of patellofemoral pain syndrome. Knee Surg Relat Res. 2021;33(1):39-39.
Surgery is reserved for select cases which have obvious structural lesions and/or are refractory to conservative management. Techniques will depend on underlying pathology but includes arthroscopy, lateral release, MPFL reconstruction, and anteromedialization of the tibial tubercle.
There are many rehabilitation protocols for PFPS. When returning to sport, most athletes must consider or meet several conditions including no effusion/swelling, no pain with squatting, proper gait, no hamstring tightness, proper core strength, good performance on functional testing and the athlete must feel ready to return.[10]Halabchi, Farzin, et al. “Patellofemoral pain in athletes: clinical perspectives.” Open access journal of sports medicine 8 (2017): 189.

Patients generally have a good prognosis although few are ever completely asymptomatic. In one study of chronic PFPS, about 2/3 of patients had complete recovery at 7 years and the other 1/3 had persistent complaints.[11]Kannus P, Natri A, Paakkala T, et al. An outcome study of chronic patellofemoral pain syndrome. Seven-year follow-up of patients in a randomized, controlled trial. J Bone Joint Surg Am … Continue reading Several factors can help predict poor long term outcomes including PFPS more than 2 months, anterior knee pain score <70, increased levels of required rest, high/ worst activity related pain.[12]ollins NJ, Bierma-Zeinstra SM, Crossley KM, van Linschoten RL, Vicenzino B, van Middelkoop M. Prognostic factors for patellofemoral pain: a multicentre observational analysis. Br J Sports Med. … Continue reading Long term complications include patellofemoral osteoarthritis, and inability to return to sport, the latter of which is seen in around 25% of athletes.[13]Rathleff MS, Rasmussen S, Olesen JL. Unsatisfactory long-term prognosis of conservative treatment of patellofemoral pain syndrome. Ugeskr Laeger. 2012;174(15):1008–1013

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