Assessing the anterior knee: part 2
Once we are confident that we have nailed down the diagnosis, having successfully excluded concomitant pathology (see assessing the anterior knee: part 1), we need to turn our attention to identifying what components of an individual’s presentation we plan to treat. For individuals with PFP, these deficits most commonly fall under four domains, with some additional confounding factors that need to be included within your clinical reasoning.
This post aims to introduce you to these domains and get you thinking about the confounding factors. Once these deficits have been identified, you can delve into your treatment tool box to pick the most appropriate approach(es) to deliver patient centred treatment.
Introducing the four domains
When presenting the findings of the subjective and objective examination back to patients, the explanation might go something like this:
“Having listened to your story and assessed your knee, the findings are consistent with a diagnosis of knee cap pain. What we know about knee cap pain is that there are four broad domains that we aim to target with treatment. For some, the way in which they are built – their structure - plays an important part in why they have developed symptoms and why those symptoms persist. For others it is how they move about how they are built – a term called biomechanics – which includes your pattern of movement as well as your strength. At times knee cap pain results from having done too much too soon, or having made a training error (volume, frequency, intensity). Finally, because we are human and pain is an experience of our body and brain – psychosocial factors act as a volume switch for the signals coming from the knee. What we are seeing here is that factor(s) x ± y ± z are important to address with treatment. This is how we plan to do it [insert treatment plan here].”
Clinical examination and imaging can give clinicians information about an individual’s structure. Local to the knee, observation in both standing and sitting (knee at 90˚ flexion) can give you indications of a high riding patella (patella alta, reported to be associated with symptom persistence beyond two years). Distally you may also observe a coupling between an everted rearfoot and an internally rotated femur that persists during dynamic function (e.g. a single leg squat). We know that the correlation between static position and dynamic function is limited, but this does not mean it is irrelevant – so observation of these characteristics should be taken into consideration. Femoral anteversion can contribute to an internally rotated lower limb position, evaluated clinically using Craig’s test which has been reported to demonstrate a moderate level of agreement with MRI.
MRI imaging and PFP have been most extensively evaluated by the team at Erasmus University in Rotterdam. Whilst they have previously reported that articular cartilage composition does not differ between individuals with and without PFP, their subsequent study has identified characteristics that appear to be associated with symptom persistence beyond two years. These features have included a higher Insall-Salvati ratio (patella alta), a smaller sulcus angle and smaller trochlear angle. In short, the less congruent the retropatellar facets and the trochlea are, the increased likelihood of symptom persistence. If you are fortunate to have this information to hand at your initial consultation, discussion about these factors can help to manage expectations, set more realistic goals in the short and medium term, and facilitate discussion about the importance of optimising the other domains to offset the structural deficits that cannot be directly addressed with rehabilitation.
The interaction between the individual’s structure and how they move about this structure has been the primary focus of PFP research for a number of years. This is at least in part because the predominate hypothesis for nociception associated with PFP has been elevated load on the retropatellar subchondral bone driven by altered movement patterns and impaired muscle function. Not to water things down too much, but the most consistent findings have been around increased dynamic knee valgus – driven by either distal or proximal deficits (or both). Both have very plausible biomechanical links to increased joint stress and should be investigated as part of your assessment. A look at functional movements can give you your first clues, progressing a squat to a single leg squat if symptoms allow, or observing the patient whilst ascending/descending stairs. A pain modification technique, changing foot movement (manually or with a prefabricated device) or facilitating hip muscle activity/hip driven movement patterns (using cues, your hands or tape) and gauging response, can be a helpful first attempt to gauge relevance of your observations.
Muscle performance tests may then follow – aiming to be tailored to the history that the patient has just shared. Pain after 10 km running? Ensure strength endurance is assessed. Pain every time the patient negotiates stairs? Power and maximal strength may offer greater insight. Strength testing does not want to be isolated to the quadriceps only, ensure the hip is assessed and the calf, ± the trunk if poor proximal control has been evident during your functional tests.
The mobility/tissue extensibility of the hip and ankle are also important measures to take, with reductions in knee bent ankle dorsiflexion associated with a knee valgus movement pattern. Significant tightness within the hip adductors and flexors can drive similar patterns.
The comparison between left and right is critical, particularly in unilaterally symptomatic individuals – with only marked asymmetries being taken into immediate and high ranking consideration. For those with bilateral symptoms it becomes a little trickier, however a pragmatic approach would be to target areas where marked deficits are evident on examination.
Volume, Frequency, Intensity
The subjective examination really gives the game away for the relevance of this domain in an individual’s pain presentation. How much activity that has been completed, on average, over the past weeks and months that preceded the onset of symptoms? How much activity has been maintained? At times the information is not forthcoming, and requires a bit of patience and some careful questioning to really explore the domain properly. During the questioning process there is great opportunity to start to use reflective questioning to help the patient understand how changes in exercise volumes may have had an impact on their symptom onset or persistence. “What impact do you think this increase in running frequency from 2-5 times per week had on your knee pain?” would be one example.
If you have heard a clear picture that points towards this domain’s importance, be sure to think about giving the patient specific tools to help them manage their training volume. These tools might include spreadsheets, training diaries, or specific rules within which they should be working – alternate days maximum, working within well-defined pain limits, ensuring symptoms have settled fully for a clear 24 hours before loading again - are all examples of how you might communicate these findings back to the patient and develop a management plan.
The relative importance of the psychosocial domain on a patient’s symptoms is established through every aspect of the assessment process. From the history that they give, the impact the pain is having on them, the way and willingness they demonstrate movement (or not), to their facial expression during certain tasks or procedures. Given that we are dealing with human beings, this domain will be relevant to everyone you see to a lesser or greater extent. As your confidence and communication improves around this domain, more relevant information will be forthcoming. A couple of central questions to be asking yourself are:
(1) in what way are these psychosocial factors impacting the person’s reported symptoms?
(2) how can these be addressed with my management planning of this individual?
By obtaining the answer to question one, you will be able to formulate a plan for question two. As an example, a patient who has come into clinic reporting pain when running that they use for stress relief, without which they find stress levels very hard to manage. It would be safe to conclude that this pattern is amplifying the nociceptive signals coming from the knee. What you then aim to do about it may be threefold:
(1) highlight the inter-relationship between elevated stress levels and an increased perception of pain;
(2) discuss how you can find other ways of achieving a natural endorphin release through a different form of exercise, that does not implicate the knee to the same extent ;
(3) using well defined limits of symptom provocation, gradually build back in running.
The clues coming from the patient can sometimes be subtle, but are often quite obvious if you look and listen! If you are in doubt, or would rather aim to quantify the contribution of this domain, asking them to complete a questionnaire can give you useful insight into what they are going through (the Orebro Musculoskeletal Pain Questionnaire, Hospital Anxiety and Depression Scale, Tampa Scale for Kinesiophobia and/ or Fear Avoidance Beliefs Questionnaire).
A comprehensive assessment remains a skill, that with appropriate reflection and effort, can be developed to give ever increasing rewards. With PFP, the important element is to develop a clinical assessment (both subjective and objective) that offers you (as the treating clinician) insight into their specific problem, providing you with the areas that could respond to treatment. Marry these findings up with our previous posts around risk factors - and our soon to come – associated factors, and you will have developed an evidence informed approach to assessing and treating this specific patient population.