Why Do I Have Knee Pain? Complete Guide to Patellofemoral Pain Syndrome: Part 5 - Factors Effecting Capacity - FITNESS PAIN FREE

Why Do I Have Knee Pain? Complete Guide to Patellofemoral Pain Syndrome: Part 5 – Factors Effecting Capacity

Patellofemoral pain syndrome (PFPS) is the most common form of knee pain treated in physical therapy clinics.  I made this series to help people better understand this condition, why it occurs and how to fix it.

In case you missed it:

Today we’ll be discussing the factors that influence the patellofemoral (PF) joint’s capacity and how that affects knee pain.

So this begs the question, what factors affect our capacity?

  1. Preparation
  2. Strength
  3. Movement Quality
  4. Psychosocial Factors
  5. Genetics and BMI

1: Preparation

We have quite a bit of newer research coming out showing that a very large predictor of injury is training volume.  If we go over a certain threshold of training volume, our risk of injury goes up (17, 18, 19).

One particularly promising area of injury prediction research is looking at spikes in an athlete’s training volume (20).  Most of this research is coming from Tim Gabbett who has studied rugby and soccer (football) athletes.  Spikes in training volume are defined as any event of training that far exceeds the typical volume of training.

It makes total sense, do way more then the body is accustomed to, we get hurt.  Tim calls this the acute to chronic workload ratio.

Basically if the acute training load (the total volume of training performed in a given week) is much larger then the chronic training load (average training volume over the past several weeks) then we’re more likely to get hurt (17, 18, 19, 20).

A few examples:

  • The athlete who begins a squat program on top of their normal training and gets knee pain
  • The athlete who begins adding running intervals into their program 2x per week in addition to their normal training and gets knee pain

Here’s the kicker, what Tim also found was that high levels of volume are actually predictive of lower risk of injury (20).

Tim found that athletes with higher VO2 max (a marker of cardiovascular fitness) and had longer preseasons were less likely to get hurt (17, 18, 19).  Basically athletes who had greater fitness and longer periods of preparation before their competitive season began were less likely to get hurt.

Athletes who were accustomed to handling a large volume of training were less likely to be injured.  This makes sense, athletes that train at a higher volume are potentially more adapted toward higher training volumes.  They are potentially creating greater “capacity” to handle these training loads and less likely to be hurt when exposed to higher volume training environments (tournaments, multi-day competitions etc.).  Remember the olympic lifting athlete described in the last article series.  She was able to increase her capacity over time to handle much larger training volumes without getting hurt.

We can take these same concepts and apply it to our injury prevention tactics.  Slowly increasing training volumes over time can increase our capacity and make us better able to handle larger and larger amounts of stress.

2: Strength

Far and away the greatest predictor of having future patellofemoral pain syndrome is having weakness with knee extension or weakness of the quads (2, 21, 22).  People with PFPS have been shown to have a 6-12% deficit in strength compared to healthy controls without PFPS (2). This makes sense, if the quadriceps are not capable of handling the stress of a given activity, the knee becomes painful.  It also seems that having PFPS creates (or increases) weakness.

Patients with PFPS tend to have weakness in the hip musculature (abduction, extension, external rotation (4). Patient with PFPS also present with reduced lateral core strength (9).  These reductions in strength also tend to correlate with dynamic valgus seen in single leg squat tasks (4).  What’s interesting is that weakness of the hips (abduction and external rotation) is NOT a predictor of future PFPS (21, 22). Some research actually shows those with great hip strength have an increased risk of PFPS (2).  It seems that weakness of the hip only occurs after already acquiring PFPS (21, 22).

It makes sense that having weakness of the hip could create poor movement during squatting and jumping maneuvers and thus PFPS but just keep in mind that the research does not support this (21, 22, 2).  Weakness of the hip is potentially not a cause but more of an effect after acquiring PFPS (2).

Side Note:  Posterolateral hip strength is NOT a good indicator of frontal and transverse hip mechanics during running or step-down maneuvers in healthy individuals (2).  In other words, having weakness in the hips doesn’t mean you’ll move poorly.  Another interesting thing observed in our medical literature is that hip strengthening does NOT improve biomechanics during single leg squat and running activities (2, 4).  These activities improve with cues and biofeedback (mirror feedback) during specific tasks and tend not to improve from task to task (improving a single leg squat does not improve running mechanics) (2, 4).  This concept will become very important when we discuss rehabilitation.

Regardless, hip strengthening has been shown to be an effective treatment for PFPS and even more so when combined with quadriceps strengthening (2, 7, 8).  Some authors theorize that hip strengthening improves the PF joint’s capacity indirectly, thus increasing the joint’s ability to handle stress and decrease pain (2, 4).

3: Movement Quality

In the last article we took an in depth look into movements at the hip, femur, tibia, ankle and foot.  We saw how these movements relate to the PF joint.  Femoral internal rotation and tibial external rotation both lateralize the stress to the knee and decrease surface area within the joint to dissipate force.  All of these things increase stress within the PF joint.  Excessive pronation at the foot (4), lack of ankle dorsiflexion (26, 27) and contralateral hip drop during single leg squatting maneuvers and jumping can all drive abnormal femoral and tibial rotation as well.

People with PFPS had more ipsilateral (same side) trunk lean, contralateral (opposite side) pelvic drop, hip adduction and knee valgus (3).  In individuals with PFPS, correcting these biomechanical faults can improve their symptoms (2, 10, 14).  Having patients go into more knee valgus, hip adduction and foot pronation has been shown to provoke these patient’s knee pain (3).  Basically, correcting these movements makes people feel better and worsening these movements creates more knee pain.

It makes sense then that keeping neutral alignment of the PF joint during movement can improve capacity of the knee.

Side Note: Only 50% of patients with PFPS present with these mal-alignment issues (4).  This means that there are probably many other factors that contribute to pain besides just altered movement.  This is also a potential reason why many athletes can have “poor” mechanics during running and never experience any knee pain.  They may have built capacity in other ways and can handle the increased stress without trouble.

Also keep in mind that as we descend deeper into knee flexion (knee bending) and as the degree of quad contraction increases we increase stress within the PF joint.  Having more knee flexion and stronger quad contractions will increase stress in the PF joint.  This will become important during rehabilitation when PF joint capacity is limited and we’re attempting to apply the right dosage of exercise to reduce pain and restore homeostasis.

4: Psychosocial Factors

Dictionary.com describes psychosocial as:

  1. Relating to the interrelation of social factors and individual thought and behavior

Psychosocial factors are things like beliefs and automatic thoughts that can drive good or bad behaviors during rehabilitation.  Social factors influence these thoughts and behaviors as well.

Patellofemoral pain syndrome is correlated with anxiety, depression, fear of movement and catastrophization (2, 25).  These are known psychosocial factors that can complicate the rehabilitation process.  These thoughts can decrease a patient’s desire to perform movements that improve pain and these negative thoughts can also sensitize our nervous system and create more pain.  These negative thoughts and behaviors can derail our best attempts to rehabilitate.

One example of a catastrophization would be:

“I can’t believe my knee hurts when I try to squat.  It will never get better and I’ll never be able to compete in weightlifting ever again”

An example of a negative belief contributing to perpetuation of pain would be:

“Having pain is a sign that my knee is not improving, is getting worse and is probably getting damaged further”

These thoughts and beliefs can be addressed through a combination of therapeutic neuroscience education and cognitive behavioral therapy.  We’ll touch on these in the next article.

Lastly, conditions such as anxiety and depression perpetuate the release of stress hormones like cortisol.  Cortisol is a hormone that can sensitize your nervous system and increase pain (28).

Obviously we know that anxiety and depression are just 2 cases that can bring a lot of stress.  Stress comes in all forms and too much can exacerbate all pain issues (not just knee pain).  Managing stress is obviously a part of this equation but so is:

  1. Adequate sleeping
  2. Proper nutrition and hydration
  3. Living a life in line with your morals, goals and dreams
  4. Practicing positive psychology and meditation
  5. Managing negative thoughts through techniques like cognitive behavioral therapy

This is an absolute behemoth of a topic that I’ll undoubtedly cover in future series but for now just keep in mind that this is all part of the capacity and pain equation.

5: Genetics and Body Mass Index

Now, half of this is either good or bad news.  We can’t really pick our parents.  Genetically we’re given a specific shape to our patella and trochlear groove.  As discussed in part 2, this is going to change from person to person.  In some people, the fit of the patella and trochlear groove just isn’t great.  In some people it is.  Ce la vie (That’s life).

The other piece of the equation is body mass index (BMI).  Body mass index is the ratio of your height to your weight.  If you’re very heavy and short then you’ve got a higher BMI.  This is something we can control.  Having a higher BMI correlates with patellofemoral pain syndrome in adults only (23).  For some reason BMI is not correlated with PFPS in adolescents (23).  Either way, it makes sense.  The heavier you are, the more stress will go through the PF joint every time you use your lower body.

So what gives our patellofemoral joint the greatest capacity?

  1. Proper programming and progressive loading
  2. Lots of strength to the knee and hip
  3. Proper biomechanics during lifting, running and moving
  4. A positive psychosocial approach with plenty of recovery mechanisms in place for the body and mind
  5. Great genetics (better pick good parents) and keeping bodyweight (BMI) in check

Now let’s take this information and bring it back to our runner examples earlier in the article series.  If you remember, “runner B” got injured.  “Runner B” also had less capacity then runner A.  Maybe “runner B”:

  • Did not prepare herself to run the marathon as thoroughly as “runner A”
  • Had less quadriceps strength than “runner A”
  • Had dynamic valgus of the knee during running
  • Was dealing with a recent divorce and bout of depression during training and the race
  • Has a more shallow trochlear groove than “runner A”
  • Was only sleeping 5-6 hours per night
  • Was carrying around a few extra pounds more then what is considered a normal BMI

Any of these factors could have decreased her capacity and increased her risk of injury.  Hopefully now you can see that getting injured is a multi-factorial process.  It’s often not 1 single factor (technique, strength, mobility) that leads to an injury.  All of these factors are probably relevant.

So to recap:

  • Patellofemoral pain syndrome is influenced by our knee’s total “capacity”
  • High levels of capacity can buffer against injury
  • PF joint capacity is influenced by a variety of factors
  • Whether or not you experience knee pain depends on a complex interaction of all of these factors

The other goal of this article series was to show you all of the factors that lead to a healthy homeostasis of the knee.  When we have knee pain from patellofemoral pain syndrome the homeostasis of the knee is off.  In order to get out of pain we’ll need to improve capacity again.  In the next article we’ll go over how we can tweak these 5 factors to get out of pain and back to training.

Click HERE for Part 6:

Knee pain is the best pain,

Dan Pope DPT, OCS, CSCS, CF L1

Works Cited:

  1. Current Concepts and Treatment of Patellofemoral Compressive Issues IJSPT 2016 https://www.ncbi.nlm.nih.gov/pubmed/27904792
  2. Current Concepts in Biomechanical Interventions for Patellofemoral Pain IJSPT 2016 https://www.ncbi.nlm.nih.gov/pubmed/27904791
  3. Examination of the Patellofemoral Joint IJSPT 2016 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5095938/
  4. Biomechanics and pathomechanics of the Patellofemoral Joint IJSPT 2016 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5095937/
  5. Salsich GB, Perman WH. Patellofemoral joint contact area is influenced by tibiofemoral rotation alignment in individuals who have patellofemoral pain. J Orthop Sports Phys Ther. 2007;37(9):521-528.
  6. Tibiofemoral and Patellofemoral Mechanics are Altered at Small Knee Flexion Angles in People with Patellofemoral Pain https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3425715/
  7. Kay M Crossley, Marienke van Middelkoop, Michael J Callaghan, Natalie J Collins, Michael Skovdal Rathleff, Christian J Barton, 2016 Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 2: recommended physical interventions (exercise, taping, bracing, foot orthoses and combined interventions) BJSM http://bjsm.bmj.com/content/early/2016/05/31/bjsports-2016-096268
  8. Christian John Barton, Simon Lack, Steph Hemmings, Saad Tufail, Dylan Morrissey, The ‘Best Practice Guide to Conservative Management of Patellofemoral Pain’: incorporating level 1 evidence with expert clinical reasoning BJSM 2015http://bjsm.bmj.com/content/49/14/923#T
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  10. Factors associated with patellofemoral pain syndrome: a systematic review. BJSM 2013 https://www.ncbi.nlm.nih.gov/pubmed/22815424
  11. The Pathophysiology of Patellofemoral Pain Syndrome – Scott Dye http://prdupl02.ynet.co.il/ForumFiles_2/19447772.pdf
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  13. 2016 Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 1: Terminology, definitions, clinical examination, natural history, patellofemoral osteoarthritis and patient-reported outcome measures” in Br J Sports Med, volume 50 on page 839.
  14. Trunk and lower extremity segment kinematics and their relationship to pain following movement instruction during a single-leg squat in females with dynamic knee valgus and patellofemoral pain. 2015 https://www.ncbi.nlm.nih.gov/pubmed/24836048
  15. The Basic Science of Articular Cartilage – Sports Health 2009 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445147/
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  17. The Development and Application of an Injury Prediction Model for Noncontact, Soft-Tissue Injuries in Elite Collision Sport Athletes. (n.d.). Retrieved August 01, 2016, from https://www.researchgate.net/publication/46288877_The_Development_and_Application_of_an_Injury_Prediction_Model_for_Noncontact_Soft-Tissue_Injuries_in_Elite_Collision_Sport_Athletes
  18. Relationship Between Training Load and Injury in Professional Rugby League https://www.researchgate.net/profile/Tim_Gabbett/publication/49775412_Relationship_between_training_load_and_injury_in_professional_rugby_league_players/links/551894590cf2d70ee27b41ad.pdf
  19. Training and game loads and injury risk in elite Australian footballers. (n.d.). Retrieved from https://www.researchgate.net/profile/Brent_Rogalski/publication/234699103_Training_and_game_loads_and_injury_risk_in_elite_Australian_footballers/links/53dadd6b0cf2a19eee8b3f9f.pdf
  20. The acute:chronic workload ratio predicts injury: high chronic workload may decrease injury risk in elite rugby league players. Retrieved from http://bjsm.bmj.com/content/50/4/231 Hulin, Gabbett, Lawson, Caputi, Sampson
  21. Prospective Predictors of Patellofemoral Pain Syndrome: A Systematic Review With Meta-analysis. Sports Health 2012
    https://www.ncbi.nlm.nih.gov/pubmed/23016077
  22. Factors associated with patellofemoral pain syndrome: a systematic review. BJSM 2013 https://www.ncbi.nlm.nih.gov/pubmed/22815424
  23. Is body mass index associated with patellofemoral pain and patellofemoral osteoarthritis? A systematic review and meta-regression and analysis. BJSM 2017 https://www.ncbi.nlm.nih.gov/pubmed/27927675
  24. Is Knee Pain During Adolescence a Self-limiting Condition? Prognosis of Patellofemoral Pain and Other Types of Knee Pain. AJSM 2016 https://www.ncbi.nlm.nih.gov/pubmed/26792702
  25. The psychological features of patellofemoral pain: a systematic review. BJSM 2017 https://www.ncbi.nlm.nih.gov/pubmed/28320733
  26. The Association of Ankle Dorsiflexion Range of Motion With Hip and Knee Kinematics During the Lateral Step-down Test. JOSPT 2016
    https://www.ncbi.nlm.nih.gov/pubmed/27686412
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  28. Stress and Your Body: The Great Courses by Robert Sapolsky
  29. Effectiveness of Manual Therapy on Pain and Self-Reported Function in Individuals With Patellofemoral Pain: Systematic Review and Meta-Analysis JOSPT 2018 https://www.jospt.org/doi/pdf/10.2519/jospt.2018.7243
  30. Effectiveness of hip muscle strengthening in patellofemoral pain syndrome patients: a systematic review https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4518569/
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  32. Differences in pressure pain threshold among men and women after foam rolling. https://www.ncbi.nlm.nih.gov/pubmed/29037655
  33. Managing Chronic Pain – John Otis: Treatments that Work
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  35. Nonspecific Low Back Pain and Return to Work https://www.aafp.org/afp/2007/1115/p1497.html#sec-7
  36. Therapeutic Neuroscience Education – Adriaan Louw

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