Patello-Femoral Pain

( Knee-Cap Pain )

Patello-Femoral Pain

Is usually caused by something wrong under or around the kneecap. There are many different causes. It can be difficult to identify the specific cause or causes, and sometimes more difficult to solve the problem. In fact, when it comes to surgery for patello-femoral pain, the outcome is more unreliable than for more straight-forward problems such as a cartilage tear, and some residual discomfort is to be expected. Patello-femoral pain is also sometimes called anterior knee pain, patello-femoral syndrome, or chondromalacia patellae.

Nature and Site of Pain

Patello-femoral pain is typically felt in the front of the knee as an ache and/or sharp pains behind or under the kneecap. The pain may often be felt around to the inner aspect of the knee and also to the outer side or even referred through to the back of the knee. Sometimes the pain can be in more than one of these areas, so it could be felt at the front and side, on both sides, or even all over the knee.

Aggravating Factors

The pain is made worse by bent knee activity such as stairs and slopes (particularly going down). Pain is often bad on kneeling or squatting. The knee can ache for hours or even a day or two after aggravation by bent knee activity. Sitting with the knee bent for some time, such as at the movies or on a long drive, can also be expected to cause aching. The knee may also be stiff and sore on getting going from rest and especially on getting up first thing in the morning.

Associated Synovitis

The knee may become swollen with fluid the day after aggravation or at the end of each day. This indicates that the joint lining is inflamed (synovitis), as a result of the irritation within the knee. Sometimes the synovitis may be due to some other problem in the knee such as a meniscus tear, but the synovial impingement may be the main source of pain. The secondary synovtis may be the reason for the patello-femoral pain, especially as the most sensitive part of the knee is the synovium (joint lining) in the front inner corner of the knee. In addition to aching with or without swelling, there may be sharp impingement pain in that area.

Buckling/Giving Way

When sharp pain occurs under the kneecap, this can cause the quadriceps muscles in the thigh to be inhibited, and to go on strike for a split second. This can cause the knee to just give way suddenly, even with walking along in a straight line. It can be bad enough to almost fall, but rarely bad enough to actually fall to the ground. Such an impingement episode may be quite painful, and aggravate the knee for some time afterwards. This is a different kind of instability from that which occurs when the knee gives way and goes out of place with twisting or landing movements, causing a fall to the ground and severe pain afterwards.

Causes of Patello-Femoral Pain

There are many possible causes of patello-femoral pain and two or more often co-exist.

Joint Surface Damage/Chondromalacia/Minor Kneecap Arthritis

There may be softening (chondromalacia), breakdown and roughness, or wear of the gristle lining (articular cartilage), of the back of the knee-cap and/or of the groove (trochlea), that the kneecap glides in. This can occur in the teenage years and right through to old age. While there is often a feeling of roughness or even noisy crunching, treatment may not be warranted if there is little or no pain, and no progression of the problem. The breakdown that occurs in the teens and twenties (chondromalacia), tends to occur partly due to a family predisposition and partly due to inadequate muscle control or mal-alignment of the kneecap, causing shear forces in the articular cartilage. In middle age and older, it tends to be more of a wear and tear process, and perhaps part of a general arthritic process slowly developing in the knee. It may due excessive tightness on the outer side of the knee causing excess pressure affecting the knee-cap.

Joint Lining Inflammation (synovitis) and/or Impingement

The synovium (joint lining) can get caught, especially underneath the lower end of the patella, and suffer sharp pains like a nerve being pinched. This may be due to overgrowth or irritability of the tip of the fat pad or formation of scar tissue from prior injury, over use, or surgery. Irritation of the tip of the fat pad can occur on its own, or in response to any cause of inflammation in the knee, including a torn cartilage or arthritis. In those situations the fat pad usually settles once the underlying cause is corrected but occasionally it can get caught in a vicious cycle of impingement causing persisting inflammation and swelling or overgrowth, which in turn, predisposes to further episodes of impingement.

Fat Pad Induration

Sometimes the fat pad that fills the space under the knee-cap, behind the patella tendon, can become so bruised or inflamed that it becomes chronically thickened (indurated) and warm. This is a particularly frustrating and difficult problem. While treatment can be given to try to control the inflammation and pain, it is usually the case that the problem takes 5-6 months to finally settle of its own accord. In the meantime, the thickening and scarring (fibrosis) within the fat pad may tether the patella so that it is not possible to lock the knee straight under muscle control, even though it may still go straight passively. It is hard work to push on with strengthening and bending exercises, and physiotherapy to prevent the knee-cap getting contracted downwards (Patella baja or infera). The fat pad may not completely settle, and if there is persisting catching pain of residual scar tissue within the knee, a further arthroscopy might be considered to trim that, but at the risk of setting off the same problem again.

Even if there is no impingement and sharp pain, synovitis can cause a lot of aching around the front of the knee, which can be worse after activity, at night, and with sitting still or driving for some time.

Plica Problems

Plicae are small membranes or folds of synovium left over from the early development of the knee. They can become tight and/or inflamed after injury or overuse, especially in sports that require a lot of bending (eg cycling, rowing, netball). They can cause anterior knee pain if they become irritated.

This is just a specific variation on the theme of synovial impingement as discussed above.

Excess Lateral Pressure Syndrome/Chronic Patella Sublaxation

This condition can cause aching in the knee, usually felt at the front, but often on one or both sides. Excessive pressure on the knee-cap can be due to tight quadriceps and hamstring muscle groups, general overuse, or to a specific condition of Excess Lateral Pressure Syndrome (ELPS). This is a condition that just develops by itself from the teenage years due to the outer check-rein (lateral retinaculum), of the kneecap being too tight and pulling the outer half of the patella down too tightly onto the outer half of the trochlea groove. It is just the way your knee is made. When this is the cause, the lateral patella retinaculum can be felt to be tight on examination of the knee and is often tender. This condition often occurs without being painful and can come to light with some other minor injury to the knee such as a simple knock or even just overuse. Similarly, it can become a problem after surgery for an unrelated condition within the knee such as a torn cartilage. Excess Lateral Pressure Syndrome can eventually lead to arthritis of the patello-femoral compartment of the knee if untreated. This condition is often associated with tightness in the Ilio-Tibial Band (ITB)which runs all the way from the outer side of the hip to the outer side of the knee.

Other Causes

There are many other possible causes of anterior knee pain than the specific patello-femoral problems that have been listed here. Other problems include such things as pre-patellar bursitis (“housemaid’s knee”), or pain that can be referred from the thigh or the hip, or nerve pain. A thorough assessment by an expert professional should be able to sort out the contributing factors.

Treatment Options

The aim of treatment is to recognise and try to treat all aspects of the patello-femoral joint that may be contributing to the pain. Often there are multiple contributing factors.

Activity Modification, Advice and Reassurance

The first thing is to understand what is causing the pain and whether you are doing any further damage by not having treatment. It is unusual that minor patello-femoral pain will become much worse without surgery or that it will necessarily lead to arthritis in future years.Treatment is a choice to enable a greater degree of activity with less pain. The pain can often be reduced by just doing less bending activities, so treatment is largely a lifestyle decision in all but the more severe cases.

Medication

Simple pain relief such as Panadeine is helpful. Anti-inflammatory medications (NSAID’s) can also be taken as required to keep things under control (provided that you have been assessed by a professional and reassured that no real damage is being done). NSAID’s can also be taken regularly to progressively settle synovitis and associated swelling, aching and impingement pain, when that is the primary problem, with no underlying damage causing it. Anti-inflammatory gels or creams rubbed on the knee can be somewhat effective as well, or instead of, oral tablets. Packets of over-the-counter anti-inflammatories like Nurofen and Voltaren advise against taking them for more than 2 weeks. This is so that you see a professional if a problem persists beyond that time. However, once the nature of the problem is understood, if no damage is being done, your doctor may advise you to keep taking NSAID's for some time until the problem finally settles. Fish oil, in big doses, like 10,000 mg per day, can also provide some supplementary anti-inflammatory effect, and perhaps reduce the dose of NSAID's required.

Physiotherapy

There are two basic forms of physiotherapy. Modality treatment can provide temporary or even progressive relief of pain and inflammation, while manipulative hands-on treatment can deal with underlying biomechanical problems such as soft tissue tightness (especially Excess Lateral Pressure Syndrome), or muscle imbalance. A physiotherapist with specific expertise in musculo-skeletal problems can thoroughly assess and treat all such aspects, including any contributing factors from the feet, hip or back. Often just a few visits can sort out the problem enough for you to maintain your knee. As well as stretching exercises, quadriceps strengthening exercises are very important and if the knee is too sore to make progress, a special technique of patella taping can often provide considerable pain relief, making the quadriceps strengthening exercises much more comfortable and efficient.

Cortisone Injection

Cortisone is a synthetic form of a naturally occurring hormone, and when injected into a joint works by settling inflammation. It is a much quicker and more potent way of achieving that than taking anti-inflammatories, but the benefit may or may not last. Cortisone may be used to settle down acute or chronic inflammation and swelling. Occasionally the main problem is that one small area of inflamed synovium keeps pinching, causing sharp pains and further inflammation which causes more swelling and scarring at that site, setting up a vicious cycle. An injection of cortisone into that site may be able to break that cycle and provide lasting relief. If it should provide only temporary relief, at least it will have served to confirm the site of origin of the pain which is valuable information in the event that surgery may be required.

Arthroscopic Surgery

If there is a specific mechanical, correctable problem which is the cause or major contributing factor for the pain, and if the pain is troublesome enough to warrant going through a small operation and several weeks of recovery, arthroscopic surgery is a treatment option.

Before embarking on surgery however it is necessary to have been fully assessed for all possible causes of pain, to have tried other treatments if appropriate and to understand the limitations of what is achievable through surgery. Your surgeon should be able to give you a realistic assessment of the chances of success of the procedure in your particular circumstances.

In most cases, success can be defined as achieving about a 50% improvement in symptoms. Better than that is a bonus and to become completely pain free is possible but uncommon. Depending on the specific circumstances, about 65 - 85% of people having surgery for patello femoral pain will be successfully improved by at least 50%, and about 1% will be slightly worse. The remainder take some time to get over the operation and end up only slightly better or much the same overall as before.

The time to recover from an arthroscopy is likely to be 3-6 weeks if all goes well but can take 3-6 months, especially after certain types of arthroscopic surgery such as doing a lateral release of the patella for Excess Lateral Pressure Syndrome (ELPS).

 Overall it is important to weigh up all the pros and cons of what it would be like to persevere without surgery compared to the possible outcomes of an operation.

Remember that after surgery things can and do go wrong occasionally and it is possible to end up worse. You should discuss your particular circumstances with your surgeon until you are clear on all the information required to make the right decision for you.