Patello femoral pain syndrome (PFPS) is an extremely common condition, covering a range of usually vague symptoms of pain ‘in’, ‘under’ or ‘behind’ the kneecap. We still don’t understand what causes it, but the explanation is likely to be different for each patient, and the result of a combination of factors rather than a single one.
Patello femoral pain syndrome (PFPS) patients tend to present with proprioceptive deficits and dysfunction in the way the key quadriceps muscle, vastus medialis obliquus (VMO), is firing. A rehab regime including patellar taping can reverse VMO motor-control dysfunction and reduce patellofemoral pain.
Beyond these few established facts, the research evidence rapidly runs out. While there are theories about what predisposes an individual to patello femoral pain syndrome (PFPS) – lateral patellar tracking, lower-limb malalignment, tight lateral patellofemoral structures – as yet no scientific evidence supports any of them. Moreover, evidence is lacking when it comes to ‘treatments’ to rectify any of these problems.
So what do we know, and how should our knowledge (and gaps in it) guide a practical approach to rehabilitation?
Patello femoral pain syndrome (PFPS) is the term we have come to use for non-specific pain around the patella, unable to be otherwise definitively diagnosed(1). Aggravating factors can include prolonged sitting, squatting, stairs and running. Patello femoral pain syndrome (PFPS) is often insidious in onset but it may come on after an acute incident such as a fall on to the knee(2).
Let us consider in turn the case for the main theoretical predisposing factors.
Patello femoral joint tracking is reliant on the balance of the medial and lateral static and dynamic patellofemoral stabilisers(3-5). It is believed that VMO helps to hold the patella in position by applying a medial force to counteract the lateral pull of the larger vastus lateralis (VL) muscle(6). The suggestion is that where muscular imbalance occurs, the supposedly stronger pull of the lateral structures will create the lateral tracking of the patella which is thought to play a key role in patello femoral pain syndrome (PFPS)(2).
In fact, while the trend in the literature suggests that in patello femoral pain syndrome (PFPS) patients the patella does both track and tilt laterally, the data is inconsistent(4,5,7). Patterns vary in both normal and patello femoral pain syndrome (PFPS) subjects from medial to lateral translations and/ or tilting, possibly because of the varying methodologies deployed in different studies, such as open and closed-chain exercises, static and dynamic testing and invasive and non-invasive techniques(8). Data consistency has almost certainly suffered because of the range of people likely to present with patello femoral pain syndrome (PFPS) and variations in bony and soft-tissue structures.
Grabiner et al(8) have suggested that abnormal lateral patellar tracking may be associated with changes in magnitude, distribution and patterns of patellofemoral joint contact pressures. Clearly we are going to need further research to measure tracking accurately and hence determine if there is a relationship between specific tracking patterns, joint contact pressures and patello femoral pain syndrome (PFPS).
Puniello(5) advocates the incorporation of iliotibial band (ITB) and tensor fascia lata (TFL) stretches and medial patellar glides into treatment and home programmes to improve patellar tracking, although there is no direct evidence to support this. Similarly there is no evidence to support McConnell’s proposition(9) that stretches of the hamstrings, lateral patellar retinacular structures and anterior hip structures may improve patellar tracking and hence VMO activation.
There is nothing in the literature to link the bony predisposing factors (Table 1 below) to PFPS(2,9,10).
|Region||Soft-tissue structures||Bony alignment|
A radiology study showed no association between patello femoral pain syndrome (PFPS) and alignment of the femur, tibia and patella(11). Thomee et al(12) showed no differences between the biomechanics of patients with patello femoral pain syndrome (PFPS) and normal subjects. Here, again, we have to conclude that we need more research to determine if there is a relationship between lower-limb alignment parameters and the development of patello femoral pain syndrome (PFPS).
McConnell(9,10) proposes that patellar taping mechanically realigns and centralises the patella within the trochlear groove. Patellar taping is based on McConnell’s classification system describing patellar malalignment – a system which is, unfortunately, unreliable. Nevertheless, it has been shown (though not in all cases) that taping can reduce pain in patients suffering patello femoral pain syndrome (PFPS)(13,15).
Crossley(16) hypothesises that taping may work by modifying the patellofemoral joint contact pressures and/ or altering the timing of VMO. Investigations using X-ray(17) and CT scan(18) revealed that medial patellar taping does not have an impact on the static position of the patella. A recent MRI study by Pfeiffer et al(19) showed that taping did translate the patella medially but this was not maintained after exercise.
Evidence does suggest that closedchain exercises may be more beneficial than open-chain exercises in maintaining ideal skeletal alignment, by improving patellofemoral joint congruence(20); and that EMG biofeedback training and electrical stimulation of the VMO(21) may be effective.
Abnormal proprioception may predispose to patello femoral pain syndrome (PFPS) by altering the movement control and, hence, patellofemoral joint stresses, as found by Baker et al(22). Alternatively patellofemoral pain may negatively affect proprioceptive information, leading to motor control dysfunction. We don’t yet know the answer to cause and effect here.
No studies have yet been done to discover what effect sensori-motor exercises have on proprioceptive deficits and pain in patello femoral pain syndrome (PFPS) patients. Yet Baker et al(22) still suggest that ‘it would be wise, and with negligible risk of harm, for clinicians to include proprioceptive exercises in the rehabilitation of patello femoral pain syndrome (PFPS) patients.’
Evidence has now shown beyond doubt that in the presence of patello femoral pain syndrome (PFPS), VMO activation is delayed in comparison to vastus lateralis in step-up and step-down tasks, alternate heel raises and toe raises(23-26), walking and ascending/descending ramps(27). Whether this motor dysfunction leads to pain or results from pain has yet to be determined.
Three recent high-quality randomised controlled trials (RCTs) have been published that reveal positive results from physical therapy interventions specifically on patello femoral pain syndrome (PFPS) signs and symptoms(25,26,28). The patients were treated once a week for one hour over a six-week period. The programme included:
In all three studies the McConnellbased physical therapy programme significantly reduced pain from patello femoral pain syndrome (PFPS)(25,26,28) and there were significant improvements in the timing of VMO activation compared to VL.
Cowan et al’s latest RCT(26) showed that the physical therapy programme produced an automatic, untrained improvement in VMO activation during a postural task. The authors described how this could be a feed-forward adjustment from the central nervous system, initiated prior to movement to ensure adequate control of the patellofemoral joint. This finding holds important potential for the transfer of benefits from therapeutic exercise into functional tasks.
In terms of the bigger picture, however, these RCTs leave unanswered questions about which specific interventions best reduce pain and improve VMO activation, as the multi-faceted McConnellbased treatment programme makes it impossible to isolate key measures. The regime’s success may be a result of VMO motor relearning, improved proprioception and/or improved biomechanical function of the lower limb(26).
Crossley(16) hypothesises that better VMO timing could be either a neurophysiological benefit of the strengthening exercise, or an indirect benefit of pain reduction brought about by the exercises, which in turn reduces the pain inhibition that causes the VMO firing delay.
In summary, then, the scientific evidence on PFPS gives us just a few pointers about what works in terms of therapy:
The following patello femoral pain syndrome (PFPS) programme incorporates the evidence-based practices discussed above to ensure optimal rehabilitation.
Again, it must be stressed that the programme should be tailored and progressed according to each patient’s unique clinical presentation and specific sporting or functional requirements. It is also important at the outset to educate the patient about anatomy, pathomechanics and the rationale for PFPS rehabilitation.
When patients can complete five step-downs from 20cm pain-free, they should progress to functional exercises in front of a mirror, ensuring correct alignment with EMG biofeedback(9):
Exercises should be patientspecific and replicate function (eg sport, work, home) and should progress as pain and performance allow. Environments should be more unpredictable (eg grass, mats, sand) and the demands of the task progressed, aiming for autonomous motor learning via activities such as:
Progress the proprioceptive exercises to unpredictable environments and unpredictable tasks that are work-/sport-specific (eg ball throwing on wobble-board). Patient should aim to return to work, training and sport. Monitor form and alignment at all times.
Taping is an effective interim measure to remove pain during exercise in order to prevent VMO inhibition. Patients can be weaned off tape as the pain settles. Orthotics can also be prescribed, if appropriate.
Remember that the McConnell programme is multi-faceted, so rehab exercises should be complemented by: