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Patellofemoral pain syndrome, a mystery finally solved
A mechanical pain at the front of the knee, patellofemoral pain syndrome accounts for 25 to 40% of specialist consultations and mainly affects a young, athletic population. Long left without an explanation, it finds its origin in a functional gait disorder, Functional Hallux Limitus.
A mechanical pain at the front of the knee
Patellofemoral pain syndrome is defined as mechanical pain felt at the front of the knee. Compressive loading such as squatting, going up and down stairs or prolonged sitting are triggering or aggravating factors. Repetitive activities such as running make the pain flare up to the point where they can no longer be practiced.
The pain subsides with rest and is reversible, even though it can persist for quite some time after exercise, much like iliotibial band syndrome, with which patellofemoral pain syndrome can be associated.
A young, athletic population
Patellofemoral pain syndrome preferentially affects a population that is often young, active or athletic, more often female than male. In a specialist knee or sports medicine practice, it alone accounts for 25 to 40% of the reasons for consultation.
A diagnosis often made by exclusion
Pain may be the only symptom, or it may be accompanied by sensations of giving way or catching, without this amounting to patellar instability with apprehension of dislocation. Effusion is rare. The diagnosis is often made by exclusion, and radiological examinations generally show nothing abnormal, apart sometimes from a transient edema of the patellar cartilage on MRI.
No correlation has ever been established between cartilage lesions and pain. The term chondromalacia patellae is no longer used today to define this syndrome, which does not progress to osteoarthritis.
Treatment without any real consensus
Therapeutically, there is no real consensus. Many studies have shown encouraging results with a comprehensive approach based on stretching and core strengthening, and foot orthoses sometimes have a beneficial effect. Unfortunately, the improvement is often temporary and recurrences are frequent: without regular training, the pain returns and forces patients to change their sports habits and their lifestyle.
A long-controversial etiology
Patellofemoral pain syndrome remains a controversial subject, with no valid explanation as to its etiology. Predisposing factors such as constitutional hyperlaxity or a marked femoral antetorsion have been implicated, but this is a multifactorial problem. A functional disorder lies at the origin of the syndrome, and the explanation can only be found through movement analysis.
The decisive role of Functional Hallux Limitus
The loss of the physiological interarticular synchronism of gait is caused by a clinical entity that is poorly known and rarely looked for, Functional Hallux Limitus (FHL). Systematically sought for more than twenty years, FHL is present and can be diagnosed in every case of patellofemoral pain syndrome.
The mechanism
FHL causes a desynchronization of gait that leads to a delayed quadriceps contraction as the foot lands on the ground. The patella is then not pressed against the lateral facet of the trochlea as it should be: it “floats,” then is abruptly slammed against the medial facet when the quadriceps contracts, too late. Patellofemoral pain syndrome must be understood as a global dysfunction induced by FHL, which takes its toll on the patellofemoral joint.
Mapping the pain
Unlike lateral hyperpressure syndrome, the pain of patellofemoral syndrome is anteromedial and appears during exercise, particularly when running. It can be so severe that it forces the activity to stop; with rest from sport, it resolves on its own. It is explained by a transient bone edema on the medial facet of the patella, linked to the repetition of pressure and shear stresses as the foot strikes the ground.
Frequent peripheral pain
Alongside the joint pain, pain can exist around the periphery of the knee, particularly over the tendons. The most exposed are the iliotibial band (the “windshield wiper” syndrome) and the pes anserinus tendons, on the medial side of the tibial plateau. Why these tendons? Because they try to fight the excessive external rotation of the tibia combined with an exaggerated supination as the foot strikes the ground, induced by FHL. The forces are substantial because they act eccentrically, braking the movement. Patients rarely complain of this pain, but it is found consistently on palpation when looked for.
Understanding through video
Three lectures take a deeper look at patellofemoral pain syndrome, the patellofemoral joint and the link with gait analysis.
The knee: the patellofemoral joint
Clinical epidemiology and a new approach to patellofemoral pain syndrome
Research: FHL and Gait Analysis
Knee pain that won’t go away?
Look for the underlying FHL
If your anterior knee pain keeps coming back despite rehabilitation, the mobility assessment at the Centre du pied can objectively identify the FHL that may be sustaining it.
At a glance
Type of pain
mechanical, anterior
Population
young, athletic
Frequency
25 to 40% of consultations
Location
anteromedial
Imaging
most often normal
Underlying cause
Functional Hallux Limitus
Further reading
Related pages
The knee and FHL
The overview of FHL-related knee conditions, from patellofemoral pain syndrome to ACL tears.
Mobility assessment
Gait analysis on an instrumented treadmill to objectively demonstrate FHL and its impact on the knee.