PATELLOFEMORAL PAIN: All you need to know! (part 1)

By Ashish Dev

“It makes me feel quite ‘stupid’ telling a patient about the diagnosis as it makes me feel like they are thinking ‘he doesn't know what's wrong’. And then especially if it is someone who is already fairly active, strong etc I often don't know what to do treatment wise as there is no obvious target.” - BCP member (practicing clinician)

Very few conditions confuse the hell out of patients and clinicians alike more than patellofemoral pain syndrome. Right from the source of symptoms, identifying the contributing factors, modifying, and managing load, designing a rehab plan to providing the patient with a timeline for getting better is all but murky to say the least. The aim of this two-part blog is to explore this condition and I hope by the time you are done reading this you will be able to tackle this condition better as a clinician and as a patient.

WHAT IS PATELLOFEMORAL PAIN ?

 Patellofemoral pain is a fancy way of saying “kneecap” pain. “Anterior knee pain” is an umbrella term and “patellofemoral pain” is a diagnosis of exclusion. It implies that once all the other causes of kneecap pain are ruled out, what you are left with is “Patellofemoral pain syndrome”. It is described as a poorly defined pain of insidious onset around and behind the patella mainly with activities that increase the load on the patellofemoral joint like squatting, climbing up and down stairs, jumping etc. (ref).

Differential diagnosis and careful elimination of other causes of anterior knee pain is important during assessment. The subjective history (age, training history, type of sport etc) along with the objective (pain location, palpation, special tests etc) form an essential basis of a good differential. Some of the conditions to rule out are patellar tendinopathy, fat pad syndrome, ITB pain, tumors, fractures, bone stress injuries, ligaments and meniscus, Osgood- Schlatter lesion and referred pain. 

DROP THE ‘S’ FROM PFPS: STOP WITH THE ‘SYNDROME’

It has been shown that the word ‘syndrome’ has negative connotations for the patient. (ref)

Note what patients have to say:

 “Is it some sort of a disease if it’s a syndrome?”

 “He was like patellofemoral pain syndrome. I don’t know if that word syndrome around it makes you catastrophise a bit as well. We’ve got this syndrome now”

 (ref)

This condition has also been referred to as ‘chondromalacia patella’ for a very long time. It is basically a term that is used by the radiologists to describe the state of the retropatellar cartilage and we should leave this term with the radiologists.

INCIDENCE & PREVALENCE OF THE PROBLEM

 Patellofemoral pain comprises 25 % of knee injuries seen in sports medicine clinics. (ref) Patellofemoral pain can occur across the lifespan and females seem to be more affected than males. Yearly prevalence in the general population was reported as 22.7%, and adolescents as 28.9%. (ref) In high school female athletes, the prevalence was reported as 10%. (ref).

 A point prevalence of 13.5% was found in military recruits, females 15.3% and males 12.3%. (ref) 11–17% of patients who present to general practitioners are affected with patellofemoral pain. (ref) It affects about 2.5 million runners in any 1 year. It is clear that not only the incidence but more importantly the prevalence is high which basically means we are not doing a very good job as healthcare professionals with our fancy treatments and specific assessments to deal with the condition that is still prevailing!

 WHY DOES IT HURT ?

There are multiple causes that have been studied which can contribute to PFP. They can be divided into the following categories:

1. BIOMECHANICAL: Maltracking of the patella has been considered a main contributing factor that causes PFP and maintains it. It was, and sadly is, still believed that due to weakness and inactivity of the VMO, the patella can’t track normally medially during knee movements. The structures pulling it laterally are tight like the IT band which needs to be stretched and released. This sort of thinking led many clinicians down a long dark road of trying to release, massage and scrape the tight structures. However, it has now been shown that releasing the IT band and changing its length is not possible with our bare hands! (ref). In fact, this study (ref) showed that in female high school athletes with PFP, “symptom improvement did not result from a change in patellofemoral tracking, but rather from other causes.”  It came as a rude shock as well to many physios who believed that they can isolate the VMO and activate it. (ref)
2. TISSUE HOMEOSTASIS: The ‘envelope of function’ concept which is a load and frequency distribution that defines a safe range of loading (the envelope of function) for a given joint. Relative supraphysiological over or under-load can disturb the tissue homeostasis and can lead to trauma induced inflammation and repair. (ref)
3. STRUCTURAL SOURCES: It was believed that the retropatellar cartilage was responsible for the pain but it was found to be aneural. It was theorized that subchondral bone marrow edema resulted in increased pressure in the knee causing the symptoms.
4. CENTRAL SENSITISATION: This study found that young females with both current-PFP and recovered-PFP displayed altered pain mechanisms compared to controls with no history of knee-pain, despite resolution of symptoms in the recurrent-PFP group. (ref) In another study, (ref) the authors compared pressure pain threshold around the knee (local hyperalgesia) and at a site remote to the knee (widespread hyperalgesia) between female runners with and without patellofemoral pain (PFP); and  evaluated the relationship between running volume and self-reported knee function. They found that this hyperalgesia, which was related to self-reported knee function, appears to be increased by greater running volumes! So, the more they ran the more pain they felt indicating that there are more than just structures that are responsible for pain. 
5. PSYCHOLOGICAL FACTORS: This systematic review indicated that even though psychological factors like anxiety, depression, catastrophizing are evident in case of PFP but still it is considered and studied largely in mechanical terms. (ref)