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{{DISPLAYTITLE:Knee Pain (Runner's Knee)}}
[[File:Knee pain.jpg|right|thumb|300px|Knee pain is the most common injury for runners. This illustration shows the relationship between the kneecap and leg bones.]]
A pain behind the kneecap is one of the most problems for runners<ref name="RunningInjuries"/>, so much so that it is sometimes referred to as 'runners knee'<ref name="KneeRunnersKnee"/>. There is no well-established cure for this problem<ref name="PPConcepts"/>, but there are a number of things you can try and some treatments to avoid. (Note that there are other types This article looks at the possible causes of knee pain in , the treatment options, and around the things to avoid. While runners are often thought of as having more kneeproblems than non-runners, but this article only looks at pain behind is probably not the kneecap, more properly called Patellofemoral case<ref name="MillerEdwards2014"/>. You might also have [[Iliotibial band syndrome| pain syndrome on outside of your knee]] or PFPS,) [[Medial Knee Pain| pain on the inside of your knee]].
=Causes=
There are a number of possible root causes of knee pain.
==Excessive stress==
The kneecap is an amazing structure, but like all body parts, it has limits in the load it can take. This overload may be due to a number of factors.
* '''Low [[Cadence]]'''. Having a low [[Cadence]] results in more vertical movement, and thus higher landing forces. This is a relatively easy fix and fixing your Cadence has many other benefits.
* '''Obesity'''. Obviously being overweight puts more stress on the knees and is linked to knee pain<ref name="KneeObesity"/>.
* '''Bad [[Running Form]]'''. Problems with [[Running Form]] can increase the landing forces and cause injury.
** '''Overstriding'''. [[Overstriding]] is''' '''landing with the foot ahead of the hip, can increase the landing forces and cause injury<ref name="KneeOverstride"/>.
** '''Heel strike. '''Landing with the weight on the heel of the foot creates a greater peak force than landing so the weight is taken by the midfoot or forefoot<ref name="KneeForefoot"/>. See [[Foot Strike]] for more details.<br style="clear: both" />
* '''Highly cushioned shoes'''. Counterintuitively, the more cushioned your shoes are, the greater the loading force on your knees<ref name="ref9"/><ref name="ref10"/>. See [[The Science of Running Shoes]] for more details. * '''Motion control shoes'''. There is evidence that motion control shoes cause more pain for all runners, regardless of their arch height<ref name="RyanValiant2010"/>. See [[The Science of Running Shoes]] for more details.
[[File:Knee Stress.png|none|thumb|400px|The stress on the knee can be a single heavy overload, or it can be a lighter stress applied many times. The green area is the area of safe functioning, and its upper limit is the blue line. The yellow area is where damage will occur to the knee, and the red area is where the damage becomes catastrophic. Note the gray area in the lower left where inactivity also causes knee damage.]]
==Inactivity==
The human body needs activity to remain healthy, and the knee is a prime example of this. Animal studies have shown than complete immobilization of the knee can result in a 50% reduction in the cartilage thickness within weeks<ref name="KneeInactivity"/>. Thankfully this damage appears to be reversible.<br style="clear: both" />
==Weak Quads==
It is common for people with knee pain to have weak quads<ref name="PFClinical"/>. However, I have found no research to suggest that weak quads are a cause of knee pain, a rather than a result of knee pain. I believe that it is more reasonable to conclude that knee pain results in less exercise as the patient avoids activities that cause pain, and thus the quads become weaker through inactivity.
==Maltracking/malalignment==
The kneecap moves in a groove in the thigh bone (femur), and it is widely believed<ref name="KneeRW"/> that if the kneecap does not track in this grove it will rub on the sides and cause knee pain. While this belief is not well supported by the evidence<ref name="patellaralignment"/>, the following underlying problems may still cause knee pain through other mechanisms.
A baker's cyst causes pain behind the knee joint rather than under the knee cap.
==ITBS==
Another common source of knee pain is [[Iliotibial band syndrome]] which generally causes pain to the outside of the knee. However, this can sometimes be confused with kneecap pain.
==Fracture==
A fracture of the kneecap will obviously cause knee pain, but is normally the result of trauma. If you suspect you have a fractured kneecap, seek medical help.
==NSAIDs==
Cartilage destruction is a major cause of concern with NSAIDs<ref name="KneeNSAID"/>, but I found no long term studies that link NSAID use with knee problems, so it's not clear if this is a widespread cause of knee pain. See [[NSAIDs and Running]] for more details.
==Chondromalacia==
The term Chondromalacia means soft cartilage and was once thought to be a common cause of knee pain. However, studies have shown that people with advanced Chondromalacia can be pain free<ref name="PPConcepts"/>.
==Leg length discrepancy==
A difference in leg length can be a factor in knee pain<ref name="PFClinical"/>. If you're concerned about having a possible leg length difference, it's best to get this evaluated by a specialist as misalignment of the hips can give the appearance of different leg lengths.
=Treatments=
This list is roughly in order of the viability and priority of the treatments.
* '''Cadence'''. If you're cadence is too low it can cause various problems, and should be optimized to around 180 steps per minute (90 steps/min for each leg). See [[Cadence]] for more details.
* '''Reduce Knee Stress'''. Stress on the knee should be reduced to prevent further damage<ref name="PFClinical"/>. Personally, I do not believe in complete rest, but prefer reduced exercise, trying to avoid or minimize pain as I believe the exercise promotes healing.
* '''Ice'''. The use of ice will not remove the underlying cause of knee pain, but it can help with recovery and healing. See [[Cryotherapy]] for more details.
* '''[[Massage]] the [[VMO]]'''. While the evidence for weak quads and [[VMO]] is marginal, massaging the [[VMO]] is easy and reasonably risk free. While the [[Foam Roller]] is good for massaging most of the quads, it tends not to get to the [[VMO]], and if the [[Foam Roller]] is your only quad massage technique then it's possible that your [[VMO]] is suffering from neglect. I would recommend using [[The Stick]] as well as using your elbow on the [[VMO]]. I've also found that using an electronic muscle stimulator on the [[VMO]] can help. See main article on [[Massage]] for more details.
* '''[[Massage]] the glutes.''' Weak glute muscles have been linked to knee pain<ref name="KneeHip"/><ref name="Glutes"/>, so massaging them may help them recover their strength and functionality.
=Anti-treatments=
The following 'treatments' are not recommended.
* '''Quad resistance training'''. A common recommendation is to strengthen the quad muscles to improve the tracking of the kneecap, especially the [[VMO]]. However, resistance training of the quads puts extra strain on the kneecap and can cause a worsening of the symptoms<ref name="PPConcepts"/>. Any strengthening of the quads should focus on the VMO.
* '''Surgery to correct mistracking'''. A study of knee pain indicated that this type of surgery has the second highest failure rate<ref name="PPConcepts"/>.
* '''NSAIDs'''. Using NSAIDs does not generally improve healing, can mask symptoms and is a cause of cartilage damage<ref name="KneeNSAID"/>. An animal study showed that Asprin resulted in greater cartilage degeneration<ref name="KneeAsprin"/>. More at [[NSAIDs and Running]].
<ref name="KneeRunnersKnee">Runner's Knee (Patellofemoral Pain) - OrthoInfo - AAOS http://orthoinfo.aaos.org/topic.cfm?topic=a00382 </ref>
<ref name="RyanValiant2010">M. B. Ryan, G. A. Valiant, K. McDonald, J. E. Taunton, The effect of three different levels of footwear stability on pain outcomes in women runners: a randomised control trial, British Journal of Sports Medicine, volume 45, issue 9, 2010, pages 715–721, ISSN [http://www.worldcat.org/issn/0306-3674 0306-3674], doi [http://dx.doi.org/10.1136/bjsm.2009.069849 10.1136/bjsm.2009.069849]</ref>
<ref name="MillerEdwards2014">Ross H. Miller, W. Brent Edwards, Scott C. E. Brandon, Amy M. Morton, Kevin J. Deluzio, Why Don't Most Runners Get Knee Osteoarthritis? A Case for Per-Unit-Distance Loads, Medicine & Science in Sports & Exercise, volume 46, issue 3, 2014, pages 572–579, ISSN [http://www.worldcat.org/issn/0195-9131 0195-9131], doi [http://dx.doi.org/10.1249/MSS.0000000000000135 10.1249/MSS.0000000000000135]</ref>
</references>
