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A pain behind the kneecap (Patellofemoral pain syndrome or PFPS) is one of the most common 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. This article looks at the possible causes of knee pain, the treatment options, and things to avoid. While runners are often thought of as having more knee problems than non-runners, this is probably not the case<ref name="MillerEdwards2014"/>. This article focuses on pain behind the kneecap (Patellofemoral Pain), but you might have [[Iliotibial band syndrome| pain on outside of your knee]] or [[Medial Knee Pain| pain on the inside of your knee]].

* '''==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 [[File:Knee StressCadence]]'''.png|center|thumb|300px|The stress on the knee can be Having a single heavy overload, or it can be low [[Cadence]] results in more vertical movement, and thus higher landing forces. This is a lighter stress applied relatively easy fix and fixing your Cadence has many timesother benefits. The green area is * '''Obesity'''. Obviously being overweight puts more stress on the area of safe functioning, knees and its upper limit is the blue line. The yellow area is where damage will occur is linked 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 damagepain<ref name="KneeObesity"/>.]]** '''Low [[Cadence* '''Bad [[Running Form]]'''. Having a low Problems with [[CadenceRunning Form]] results in more vertical movement, and thus higher can increase the landing forcesand cause injury. ** '''Highly cushioned shoesOverstriding'''. Counterintuitively, the more cushioned your shoes are[[Overstriding]] is''' '''landing with the foot ahead of the hip, can increase the greater the loading force on your kneeslanding forces and cause injury<ref name="ref9"/><ref name="ref10KneeOverstride"/>. ** '''ObesityHeel strike. '''. Obviously being overweight puts more stress Landing with the weight on the knees and heel of the foot creates a greater peak force than landing so the weight is linked to knee paintaken by the midfoot or forefoot<ref name="KneeObesityKneeForefoot"/>. See [[Foot Strike]] for more details.<br style="clear: both" />** '''Bad running formHighly cushioned shoes'''. Problems with running form can increase Counterintuitively, the more cushioned your shoes are, the landing forces and cause injury.*** '''Overstriding. '''Overstriding is''' '''landing with greater the foot ahead of the hip, can increase the landing forces and cause injuryloading force on your knees<ref name="ref9"/><ref name="KneeOverstrideref10"/>. (See [http://runningtimes.com/Print.aspx?articleID=23217 See Are You Overstriding?] and [http://runningtimes.com/Article.aspx?ArticleID=20271 An Analysis The Science of Running TechniqueShoes]] for more details on overstriding.)*** '''Heel strike. Motion control shoes'''Landing with the weight on the heel . There is evidence that motion control shoes cause more pain for all runners, regardless of the foot creates a far greater peak force than landing so the weight is taken by the midfoot or forefoot their arch height<ref name="KneeForefootRyanValiant2010"/>. * '''Inactivity'''See [[The Science of Running Shoes]] for more details. [[File:Knee Stress. png|none|thumb|400px|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 stress on the knee can result in be a 50% reduction in single heavy overload, or it can be a lighter stress applied many times. The green area is the cartilage thickness within weeks<ref name="KneeInactivity"/>area of safe functioning, and its upper limit is the blue line. Thankfully this The yellow area is where damage appears will occur to be reversiblethe knee, and the red area is where the damage becomes catastrophic.<br styleNote the gray area in the lower left where inactivity also causes knee damage.]]==Inactivity=="clear: both" />* '''Weak Quads.''' It The human body needs activity to remain healthy, and the knee is common for people with knee pain to have weak quads<ref name="PFClinical"/>a prime example of this. However, I Animal studies have found no research to suggest that weak quads are a cause shown than complete immobilization of the knee pain, can result in a rather than a result of knee pain50% reduction in the cartilage thickness within weeks<ref name="KneeInactivity"/>. I believe that it is more reasonable Thankfully this damage appears to conclude that knee pain results in less exercise as the patient avoids activities that cause pain, and thus the quads become weaker through inactivitybe reversible.<br style="clear: both" />* '''Maltracking/malalignment. '''[[File:Kneecap==Weak Quads==It is common for people with knee pain to have weak quads<ref name="PFClinical"/>.png|center|thumb|200px|A cross section However, I have found no research to suggest that weak quads are a cause of the kneecap and femor (thigh bone) showing how the kneecap fits in knee pain, rather than a grooveresult of knee pain.]] The kneecap moves in a groove in the thigh bone (femur), and I believe that it is widely believed<ref name="KneeRW"/> more reasonable to conclude that knee pain results in less exercise as the patient avoids activities that if cause pain, and thus the kneecap does not track quads become weaker through inactivity.==Maltracking/malalignment==The kneecap moves in a groove in this grove it will rub on the sides thigh bone (femur), and cause knee pain. However, this belief it is not well supported by the evidencewidely believed<ref name="patellaralignmentKneeRW"/>. ** '''Weak [[VMO]].''' The alignment of that if the kneecap is does not related to the overall strength of track in this grove it will rub on the quads, but rather an imbalance of the muscles that make up the quadssides and cause knee pain. [[File:Vastus medialis muscle short.jpg|center|thumb|200px|The Vastus Medialis Obliquus or [[VMO]], which While this belief is often blamed for mistracking of not well supported by the evidence<ref name="patellaralignment"/>, the kneecapfollowing underlying problems may still cause knee pain through other mechanisms. * '''Weak [[VMO]] ].''' The quads consist alignment of four muscles, and a relative weakness in a subdivision the kneecap is not related to the overall strength of one musclethe quads, but rather an imbalance of the Vastus Medialis Obliquus or [[VMO]]muscles that make up the quads. The quads consist of four muscles, has been linked to kneecap alignmentand a relative weakness in a subdivision of one muscle, the Vastus Medialis Obliquus or [[VMO]], has been linked to kneecap alignment<ref name="KneeLinTomo"/> and knee pain<ref name="KneeVMOAtrophy"/>.** '''[[VMO]] Delay.''' There is some evidence that people suffering from knee pain (PFPS) have a delay in the activation of the [[VMO]] compared with the main quad muscles<ref name="KneeVMODelay"/><ref name="KneeVMODelayMeta"/>, which reduced the lateral force by 25%<ref name="KneeVMODelayPower"/>. Detecting this timing difference is normally requires sophisticated clinical equipment, but there is some suggestion that the delay can be felt directly by placing fingers on the belly of the [[VMO]] and the VL<ref name="PFClinical"/>. ** '''Weak Hips.''' A weakness in the hip muscles has been linked to knee pain<ref name="KneeHip"/>. Weak hip muscles result in the leg rotating so the foot points towards the midline of the body (internal rotation), so when the leg bends extra stress is placed on the knee. <br style="clear: both" />** * '''[[Q angleAngle]]'''. The thigh bone and lower leg are not in a straight line, but form an angle at the knee called the '[[Q angleAngle]]'. A large [[Q Angle ]] is often thought to cause or contribute to knee pain, but a high [[Q angle Angle]] was only seen in 6% of knee pain (PFPS) cases<ref name="RunningInjuries"/> and a high Q angle is not associated with biomechanical knee stress<ref name="KneeQAngle"/>. [[File:Q Angle* '''Over Pronation'''.png|right|thumb|200px|If you draw an imaginary line from Pronation is the [http://en.wikipedia.org/wiki/Anterior_superior_iliac_spine front natural movement of the pelvis] to foot where the kneecap and from the lower leg arch flattens to absorb landing forces. If the kneecapfoot pronates too much, the angle between foot will lean towards the lines is midline of the Q Anglebody and the lower leg and knee will follow this motion, moving towards the midline.]]** '''Over Pronation'''. Pronation is Like weak hips, the natural movement of the foot where knee towards the midline creates extra stress on the arch flattens to absorb landing forcesknee. If [[File:Kneecap.png|none|thumb|200px|A cross section of the foot pronates too much, kneecap and femor (thigh bone) showing how the foot will lean towards the midline of the body and the lower leg kneecap fits in a groove.]] ==Arthritis==Arthritis is an inflammation of the joints and can affect the knee will follow this motion, moving towards the midline. Like weak hipsThere are various types of arthritis, and diagnosis requires X-Ray, testing the movement of fluid around the knee towards the midline creates extra stress on joint or inserting a viewing scope into the knee. * '''Arthritis'''joint. Arthritis is an inflammation outside of the joints and can affect scope of this article. ==Baker's cyst==A baker's cyst causes pain behind the knee. There are various types of arthritis, and diagnosis requires X-Ray, testing joint rather than under the fluid around the joint or inserting a viewing scope into the joint. Arthritis knee cap. ==ITBS==Another common source of knee pain is outside [[Iliotibial band syndrome]] which generally causes pain to the outside of the scope of knee. However, this articlecan sometimes be confused with kneecap pain. * '''Baker's cyst'''. ==Fracture==A baker's cyst causes pain behind fracture of the kneecap will obviously cause knee joint rather than under pain, but is normally the knee capresult of trauma. If you suspect you have a fractured kneecap, seek medical help. * '''ITBS'''. Another common source ==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 pain is [[Iliotibial band syndrome]] which generally causes pain to the outside of the knee.* problems, so it'''Fracture'''. A fracture s not clear if this is a widespread cause 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 helpSee [[NSAIDs and Running]] for more details. * '''NSAIDs'''. Cartilage destruction is ==Chondromalacia==The term Chondromalacia means soft cartilage and was once thought to be a major common cause of concern with NSAIDsknee pain. However, studies have shown that people with advanced Chondromalacia can be pain free<ref name="KneeNSAIDPPConcepts"/>, but I found no long term studies that link NSAID use with .==Leg length discrepancy==A difference in leg length can be a factor in knee problems, so pain<ref name="PFClinical"/>. If you're concerned about having a possible leg length difference, it's not clear if best to get this is evaluated by a widespread cause specialist as misalignment of knee pain.* '''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 the hips can be pain free<ref name="PPConcepts"/>.* '''Leg length discrepancy'''. A difference in give the appearance of different leg length can be a factor in knee pain<ref name="PFClinical"/>lengths.  

* '''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. * '''[[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.

* '''Footwear'''. There are two types of footwear changes that may help with knee pain that are contradictory; minimalist footwear and orthotics. Personally, I am concerned that Orthotics may help with knee pain but cause other problems, and the use of orthotics goes against the evidence for minimalist footwear. However, there is more scientific evidence to support orthotics for resolving knee pain, even though orthotics may increase knee stress. My personal belief is that it is better to cautiously move towards [[Shoes| Minimalist Running Footwear]] rather than use orthotics, but I want to be clear that there is not clear scientific support for my belief. ** '''Minimalist shoes'''. There is good evidence that running shoes increase the stress on the knee<ref name="ref14"/>, and that a more minimalist approach to footwear may be appropriate. There is plenty of anecdotal evidence<ref name="KneeMinCaseStudies"/> that minimalist footwear helps with knee pain, but only limited science<ref name="KneeMinShoes"/> to back it up. Also, changing too quickly to minimalist footwear may result in [[Too Much Too Soon]] injuries. See '[[Are your running shoes injuring youThe Science of Running Shoes]]?' for more details.

* Knee brace? * '''[[Joint Supplements]]'''. The joint supplements glucosamine and chondroitin provide marginal benefit, but are considered safe, so they may be worth considering if you can justify the expense. Other supplements such as Omega 3 oils and Vitamin C/E may be worth considering. For more details, see [[Joint Supplements? ]].* '''TapingKnee brace/sleeve/strap'''. A knee sleeve is a simple elastic wrap that goes around the knee, sometimes with a hole to avoid pressure on the kneecap. A knee brace usually provides hard plastic support in addition to the sleeve. The use of tape has been shown to be effective at reducing evidence supporting knee painbraces is limited<ref name="KneeLongTermKneeBracingBrouwer2005"/><ref name="KneeTapeBrockKneeBracing"/>, with many of the studies having poor quality<ref name="KneeTapeMcConnelKneeBracing"/>. One reasonable study showed improvement with a brace<ref name="KneeBracingPowers2004"/>, by over 90% in one studybut better quality studies showed no benefit<ref name="KneeTapeEMGKneeBracingMiller1997"/>. One study used tape to pull the knee cap towards the midline of the body<ref name="KneeTapeMedialKneeBracingLun2005"/>, others relied on evaluation to define the correct direction<ref name="KneeTapeBrockKneeBracingHunder2011"/>. The most common method mentioned is 'McConnell taping'There are even fewer studies for knee sleeves<ref name="KneeTapeMcConnelKneeSleeveBea09"/>. The only study on knee straps showed no benefit<ref name="KneeTapeBrockKneeBracingMiller1997"/>. I found no indications of the long term effects or safety of knee braces, sleeves or straps. Based on the available evidence, the use of these approaches does not seem justified. I found no studies that looked at [[A review of graduated compression wear|Compression Tights]] but they may act in a similar way to a knee sleeve and instructions can be found by Googling 'McConnell taping'they have [[Why compression clothes|other benefits]].  

* '''Quad strengtheningresistance 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.

* '''NSAIDs'''. Using NSAIDs does not generally improve healing, can mask symptoms and is considered 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]].=Surgery=Surgery for knee problems is a common treatment, but the research suggest is may not be worthwhile. While surgery and exercise seem to generally result in improved pain, function, and quality of life, it doesn't do better than a program of exercise. So far I've found no research supporting knee surgery, though most of the research I've found has been on degenerative meniscus tears and the subjects are not runners. However, it seems possible to me that knee surgery may help some subjects and harm others, with the net effect being no average benefit. ==Degenerative Meniscus Tears==While a meniscus tear is a common knee injury, the only research I could find on this condition concerns degenerative tears. * A 2012 study looked at 102 patients with a meniscus tear and compared surgery with strengthening and found no difference in terms of function or pain after two years<ref name="YimSeon2013"/>. Both groups reported a high (and similar) degree of satisfaction, with two thirds reporting complete pain relief. The exercise group was given supervised training three times per week for three weeks, then a further eight weeks of unsupervised exercise, while the surgical group only had the 8 weeks of unsupervised exercise. The exercise consisted of stretching the hamstrings and quads (1 min each), 3 x 10 reps of leg extensions, leg curls, half squats and full squats, plus 15 minutes of cycling. The squats were only for the last 3 of the 8 weeks, and all exercise was to be with some strain but almost pain free. There's no reason to believe this regime is optimal, but it's an interesting starting point. The patients had a degenerative horizontal tear and the surgery removed part of the meniscus only, but there is no indicates from the study of the proportion removed. The [http://www.orthopaedicscore.com/scorepages/tegner_lysholm_knee.html Lysholm score]for the subjects was ~65 which indicates "poor" status. * A 2013 study looked at with a meniscal tear and osteoarthritis in 351 subjects, with half randomly assigned to surgery, the others to physical therapy<ref name="KatzBrophy2013"/>. The study did not find any significant difference in functional improvement after 6 months. (30% of those assigned to physical therapy elected to have surgery before the 6 months were up. Those subjects had worse symptoms at the 2-month mark, but some of the best overall results at the end.) There were no details on the type or severity of the meniscus tear, or the percentage of meniscus removed.* A 2013 study looked at 96 subjects over five years after either surgery plus 2 months of exercise or just exercise for with degenerative meniscal tears<ref name="HerrlinWange2012"/>. No difference was found in the outcomes at the 2 and 5 year marks. It's worth noting that a third of the exercise only group still had disabling knee problems after the exercise therapy but they improved to the same level as the other subjects after surgery. * A 2013 study comparing surgery with sham surgery for degenerative meniscus tears (without osteoarthritis) in 146 subjects over 12 months found no difference between the groups<ref name="Sihvonen-2013"/>. The subjects had knee pain for more than three months prior and had not responded to conservative treatment. Both groups improved over the 12 months, but there was no difference between the groups. This is one of the highest quality studies available, with some lengths taken to blind the subjects to their knowledge of the surgery or sham surgery. There was no indication of how much meniscus was removed, though the subjects had an average Lysholm score of 60 significant problems. * A 2007 study looked at 90 subjects with degenerative meniscal tears who were given either exercise or exercise plus surgery<ref name="Herrlin-2007"/>. Both groups reported similar improvements in pain, knee function and quality of life. The exercise consisted of cycling, calf raises, leg press, stair walking, wobble board, jumping, stretching, and similar exercises to improve strength and balance. The average Lysholm score of the subjects was 65, but the range was 24-94. * A small 2012 study of just 17 subjects with an MRI-verified degenerative meniscus compared surgery (n=8) with exercise (n=9) over three months and found no difference in pain levels or knee function<ref name="ØsteråsØsterås2012"/>. However, the study did find that the surgery group had statistically more anxiety and depression. * A 2014 analysis of the available research concluded that "There is moderate evidence to suggest that there is no benefit to arthroscopic meniscal débridement for degenerative meniscal tears"<ref name="Khan-2014"/>. This review looked at seven trails (all of them noted here in more detail.) * A 2013 study compared surgery with steroid injections for degenerative meniscus tears in 114 subjects<ref name="Vermesan-2013"/>. They randomly received surgery or injections of betamethasone and lidocaine and evaluated at one month and one year. The study found only a marginal improvement in the surgery subjects over the steroid injection. However, given the evidence that surgery is no more effective than avoiding surgery, it might be better to say that steroid injections are worse than no surgery or surgery. * There are indications that meniscus surgery may increase the risk for osteoarthritis, with the amount of meniscus removed tending to predict a higher osteoarthritis risk<ref name="PapaliaDel Buono2011"/>. However, it's also possible that a meniscus tear without surgery also increases risk for osteoarthritis <ref name="EnglundGuermazi2009"/>.* A 2008 study found that 60% of subjects aged 50+ had meniscus tears<ref name="EnglundGuermazi2008"/>. The rate of meniscus tears was similar in patients with and without knee pain symptoms. What's not clear is that if you have a meniscus tear and you have knee pain, what's the chance of the two being unrelated? It seems quite possible from the data that you could have surgery for a meniscus tear that has nothing to do with your pain. ==Surgery for Other Knee Injuries==* A 2010 study of 121 young adults compared two treatment approach for acute, traumatic ACL injury<ref name="FrobellRoos2010"/>. One group received rehabilitation and surgery within 10 weeks (early group), the other group received rehabilitation with an option for surgery if required (delayed group). Only 40% of the delayed group underwent surgery, and both groups had similar success in terms of pain, quality of life, and difficulty in sports/recreational activities.* A 2008 study of arthroscopic surgery for osteoarthritis found that surgery had the same success rate as those who did not undergo surgery<ref name="KirkleyBirmingham2008"/>. The study looked at 92 surgical patients and 86 controls over 2 years, with both groups receiving 12 weeks of physical and medical therapy, including exercise. The patients were told to continue the exercise unsupervised for the rest of the study. The evaluations at 3, 6, 12, 18, and 24 months showed both groups improved a similar amount. This was a follow on to a 2002 study that had also found no difference in outcome from surgery or a placebo surgery<ref name="MoseleyO'Malley2002"/>,