Sunday, December 13, 2009

Patellofemoral Pain Syndrome- Where exactly is the pain coming from?

The knee of an athlete is often a diagnostic dilemma. The knee obtains important biomechanical function and is supported by an array of ligaments and muscles. For these reasons it can be difficult to pinpoint the specific structure which is injured. Such a concept is to be blamed for the creation of Patellofemoral Pain Syndrome (PFPS),

What exactly is PFPS?

When you think about it what exactly does this diagnosis tell you? Essentially all that this means is we know there is pain and we know it has something to do with the Patella-Femoral Joint. In my opinion this is not a real diagnosis. What if we made clinical conclusions like this for everything? Chronic Neck Pain Syndrome or Sore Elbow Disease?

In reality, PFPS is an umbrella term to describe any possible causes of pain which can be attributed to the Patella-Femoral Joint. Such as:

-Chondromalacia Patella - Softening of the cartilage under the patella
-PatellaFemoral tracking problems
-Infrapatellar Fat Pad being impinged (Hoffa's Disease)

 This is why I often tell colleagues and those which attend my seminars to not worry about the diagnosis. What you need to find out is WHAT EXACTLY IS CAUSING THIS PAIN?

Originally many used to take a structural approach to PFPS. Measurements of one's Q angle or a patient's knee valgus was observed and often chondromalacia patella was diagnosed. However, if structural abnormalities were deemed the cause how does one explain the benefits from conservative treatment? The patients Q angle has not changed. Furthermore, not everyone with a high Q angle has knee problems?

Researchers are starting to progress away from the structural approach of PFPS and asking what is actually causing the pain?

Ok so what are my options?

A biomechanical fault, muscle imbalance or pathophysiological process which leads to:

1.Inflammation of the synovial lining
2.Inflammation of the fat pad
3.Increase in intra articular pressure

4.Hyperinnervated Lateral Retinaculum  

To fully understand you have to address the signs and symptoms

PFPS can be exaggerated with running and climbing up and down stairs. This mechanism of injury is simply due to overuse or excessive force. Such activities as climbing stairs can produce forces 3 times one's body weight. A loss of Tissue Homeostasis occurs and now the joints synovial lining becomes inflamed (#1). This concept is a pretty easy one to understand.

However, how does one explain the movie sign (Pain in the knee with a prolonged period of sitting)? One does not put excessive force through the knee as they sit. There are two leading theories for the movie sign. While sitting we may predispose our knee to change normal position and now structures my impinge a once swollen inflamed synovial lining (#1). The second theory is that as we sit our knee's intra articular pressure increases and thus creates pain (#3). Studies have shown that the knee is an extremely fibrotic and capsular entity. When put in prolonged flexion we may impede venous outflow and increase arterial blood flow to and from the knee. This change in blood flow can increase the pressure within our knee as we sit.

Reasoning for these causes of pain is the popular treatment called McConnell taping. This is a taping method which has shown to relieve pain. However, the results are not always consistent and many wonder why. It can be purposed that by taping the patella in a more neutral position we are preventing it from impinging structures and thus resolving the patient's pain (#1, #2).

Lastly a maltracking patella has also been associated with PFPS. What studies have observed is anatomically those who suffer from PFPS have a hyperinnervated lateral retinaculum. Furthermore, these subjects presented with more nociceptive fibers within the nerves. The theory is the patella tracking medially (usually) will produce tension along the lat retinaculum. Now the nerves are put under traction and start to experience myxoid degeneration. In an attempt to heal itself the body now produces more neural drive and stimulation to that area thus creating a hyperinnervated structure and pain is produced (#4).

Still Don't Believe Me?

Check out the article posted below by Scott F Dye. This is one of the most intriguing and interesting articles I have ever read. Scott which is an orthopedic surgeon (I believe?) has actually been diagnosed with chondromalacia patella in the past. He attempts to cut himself open and inspect the cause of his knee pain. When probing his patella cartilage no pain is felt. However, pain is accentuated when probing his synovial lining and Hoffa fat pad. Furthermore injecting himself with saline increases his intra-articular pressure and produced extreme pain. This article has given valuable premise to support 3/4 theories of what causes PFPS. Imagine... the things we do for science (Left probing cartilage, Right probing synovial lining).

In summary, as professionals we need to steer away from umbrella terms such as PFPS. As a student I found this diagnosis extremely confusing and more so difficult to explain to patients. It wasn't until exploring the mechanism of pain in which I become more inclined to make such a diagnosis. To create consistency in research and amongst colleagues we need to address the actual form of PFPS were discussing. In addition, exploring this notion lays great premise on how we can guide our treatment. This is one condition where the diagnosis may actually be made after treatment is initiated. Dr. Wayne Button, BSc, D.C

Dye, S., & Vaupel, G. (1994). The Pathophysiology of Patellofemoral Pain Sports Medicine and Arthroscopy Review, 2 (3), 203-210 DOI: 10.1097/00132585-199400230-00004

Sanchis-Alfonso V, & Roselló-Sastre E (2000). Immunohistochemical analysis for neural markers of the lateral retinaculum in patients with isolated symptomatic patellofemoral malalignment. A neuroanatomic basis for anterior knee pain in the active young patient. The American journal of sports medicine, 28 (5), 725-31 PMID: 11032232

Naslund, J., Walden, M., & Lindberg, L. (2007). Decreased Pulsatile Blood Flow in the Patella in Patellofemoral Pain Syndrome The American Journal of Sports Medicine, 35 (10), 1668-1673 DOI: 10.1177/0363546507303115




  1. What is your take on the biomechanical chnges that come into play with poor femoral alignment and muscular control during weightbearing? In particular, going down staris?

    Thanks Dr. Wayne!

  2. Again as stated above a biomechanical fault, muscle imbalance which leads to a pathological process. However, yes I do agree the pain might not be just due to a substantial force.

  3. I have many "nerve" symptoms associated with my PFPS...burning and tingling sensations. I also have the usual grinding with squatting and catching sensations with bicycling. My case is rather bizarre, in that squatting, kneeling, and stairs don't bother me...walking bothers me (I'd rather have it be the stairs, believe me, I could avoid those but I can't avoid walking). I often have burning and tingling at night. Would this burning and tingling be a sign of hyperinnervation? If so, what can I do about it? Accupuncture? Capsaicin? If I wear a brace or knee sleeve my pain is greatly reduced, but I wonder if this is because I am "distracting" my nerves by having something around my knee. I would do anything to be rid of my knee is very disabling.

  4. It definatly sounds like you have something nerve wise going on with the knee. These symptoms may be secondary to the actual complaint. If pain is reduced with a brace it tells me the knee prefers to be in a stable state. This is often a good indicator that if you can perform a aggresive rehab program designed to help stabilize your knee you may have some benefits.

    However, diagnosing and treating over the internet is not the best practice technique. Sometimes a first visit knee patient can take over an hour and imaging ordered. You need to get this assessed by a professional. Acupuncture may help as research is fairly good however I am not trained in acupuncture and that is as much as I can say.

    If you email me ( location I will look online and perhaps be able to recommend someone that looks adequate in their certifications.

  5. I could avoid those but I can't avoid walking). I often have burning and tingling at night. Would this burning and tingling be a sign of hyper innervation.

  6. Burning and tingling usually means a pathology of the nerve. Weather or not hyper innervation I don't know. This is more theory for why pain occurs it won't necessarly correlate to tingling and burning.

  7. Thank you for your response! I will e mail you as suggested.

  8. I have a 13 year-old daughter who was dxd a year ago with ptps. I have been incredibly frustarted with this dx because I already knew her knee hurt before all the specialists. I want to know the mechinism of her pain and specifically what is injured and or hurting. This has become chronic for her. An MRI showed minimal patellar cartilage signal heterogeneity which means mild chondromalacia as I am told. But the cartilage is not inervated so that is not hurting her. This pain occured right after a dance class and is bilteral anterior knee pain. ANy thoughts about how to deterine what is causing her pain. Any tests (such as merchant x-ray helpful? She needs to be able to live a normal life for a kid again. thanks

  9. Wow, I never realized that Patellofemoral pain syndrome was such a broad term. I have always used it to describe any kind of pain in my knee. I hurt my knee while playing soccer a couple of weeks ago, and it still hasn't healed 100%. I'll have to try out some of these exercises.

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  19. I want to know the mechinism of her pain and specifically what is injured and or hurting. This has become chronic for her. An MRI showed minimal patellar cartilage signal heterogeneity which means mild chondromalacia as I am told. But the cartilage is not inervated so that is not hurting her.

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