Knee Pain: Knee Cap Niggles

So the Commonwealth Games have finished with the marathon!! It was exciting to watch the competitors run straight past our clinic on Sunday- congrats to Michael Shelley, Helalia Johannes, Kurt Fearnley and Madison de Rozario.  Seeing these athletes completing this superhuman task is incredible, and the inspiration to amp up the exercise is great.  However, it is concerning that up to one third of recreational runners will injure themselves in some way each year. Most of these people end up seeing their GP. It got me thinking about the most common cause of pain in recreational runners. As it turns out up to 25% of these recreational running injuries present with pain behind the knee cap, or patella This is otherwise known as patellofemoral pain.  This mostly affects younger runners with the 16-25 year old age group making up 70% of all cases.  It is also a common injury presenting to sports physicians with up to 10% of their case load being patellofemoral pain.
The most common symptom that patients report is pain in front of the knee but behind the knee cap. It tends to get worse walking up and down stairs, sitting with knees bent, or while squatting or kneeling.  The good news is that, unlike arthritis patellofemoral pain is not due to wear and tear of the joint. It is also not considered to be caused by a tendinopathy or other tendon lesion such as Osgood Schlatter Disease- (wait for upcoming article).

Commonwealth Games Marathon 2018

Patellofemoral pain, also known as anterior knee pain, is currently thought to be due to increasing pressure on the joint at the front of the knee and behind the patella. This increased pressure causes inflammation to the cartilage lining the joint. Cartilage usually provides the smooth sliding surface of the patella over the femur.  For such a common injury it’s surprising that not much is actually known about he exact cause of the increased pressure.  The most up to date literature hypothesises that it could be due to a number of different causes including incorrect tracking of the kneecap in the joint, abnormal shape of the joint, imbalance of the surrounding soft tissues or weakness in the supporting muscles.
At a microscopic level the bone becomes painful due to stress on the cartilage lining the joint, resulting in increasing friction forces within the joint leading to inflamation.  This results in cartilage fragmentation and causes the cartilage to be unable to perform its job, that is, it is unable to absorb the impact of the joint when it moves. It addition to this it has been suggested that reduction in blood flow to the knee cap leading to poor oxygenation of the area may also contribute.

Commonwealth Games Marathon 2018

So…..Do you have patellofemoral pain?  This is usually a dull ill-defined ache which comes on slowly behind the kneecap.  It can be in both knees or one knee, is irritated by stairs or squatting and often associated with locking of the knee or a feeling of instability.  If you experience these symptoms you need an examination by your doctor and an X-ray to exclude more serious pathology. In addition you may also require a CT or MRI for further assessment if your doctor feels this is indicated.  Once the diagnosis is confirmed and more serious pathology, such as a fraction or tendon injury, have been excluded treatment can commence.
Treatment historically includes physiotherapy, aerobic training and use of orthotics or bracing.  Conservative treatment can be a bit hit and miss however, with 70% of patients getting a sore knee again within one year of treatment. Research has shown that orthotics, taping and bracing do not provide a predictable or consistent contribution to recovery. Many patient however do report a subjective benefit from this. Resting the knee is probably the most effective treatment with up to 30% of patient reporting improvement after one month. Emerging evidence has suggested that supervised exercise therapy can result in an improvement of function and a reduction in pain. Unfortunately, this study did not clarify the type of exercise and which part of the population of sufferers would benefit most from this type of intervention. Non steroidal anti-inflamatory drugs (eg ibuprofen) have limited evidence in their use for pain relief in these cases however are used quite often in the community for symptomatic relief. Surgery can be contemplated after a failed trial of physio but is actually quite rare. Your GP or sports medicine specialist would be most suited to assessing your individual needs and developing a treatment plan tailored specifically to you.

Excitingly there is ongoing research in this area. For example there is conflicting evidence supporting the use of glycosaminoglycan polysulphate as a possible future intervention.  Glycosaminoglycans are vey polar and will attract water, which intuitively could be helpful in lubricating the knee joint if it can be incorporated into the cartilage. It has been shown that it may have an anti-inflammatory component and may increase blood flow to synovium and bone.  This is especially interesting to me because pentosan polysulphate (Cartrophen) which is a novel glycosaminoglycan polysulphate has been used in dogs for years!  Good to know my history in Vet is also useful in sports med!!

  • GPearls on the GC;
    • Marathon runners are superhuman
    • there are hundreds of possible reasons for knee pain
    • personalised physio program produces patellofemoral perfection
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