Medial Plica Syndrome

A plica is a band or shelf of soft tissue on the inner lining of the knee.  These bands are made up of synovial tissue, which is the same tissue as normally lines the inside of the knee joint. About 15% of people have one or more significant plicae in their knee, and the most common location for a plica is on the medial side of the knee, running in a line just medial (inwards) to the medial (inner) side of the patella (kneecap). Plicae most probably represent bands of residual tissue from when the knee was growing as an embryo, where two separate compartments fuse together and the sheet of tissue between them shrinks back, to form one single knee joint compartment. When these sheets of tissue fail to shrink back fully, then this leaves behind a shelf or band (plica) that can subsequently cause problems.

If a plica is small then it is unlikely to cause any problems. If a plica is large and thick but you’re a couch potatoe and don’t do any exercise, then again the plica is likely to be irrelevant. However, if you have a large/thick plica and you do a lot of exercise (particularly running, or sometimes long distance cycling) then the plica can rub against the inner edge of the knee (on the medial edge of the medial femoral condyle). This repetitive rubbing can cause inflammation, which causes pain. When a medial plica becomes symptomatic and painful, this is called ‘Medial Plica Syndrome’.

The pain of Medial Plica Syndrome tends to be a burning pain around the anteromedial (front, inner) side of the knee that comes on specifically with exercise. With most people, their knee is fine when they first start running (or cycling), but after a certain time or distance the pain comes on. The pain gets worse if you then continue exercising, but gradually and slowly eases off if you rest.

Plicae and Plica Syndrome can occur in places other than the medial side of the knee, and other potential sites that can be affected are the lateral (outer) side of the knee and the suprapatellar region (just above the kneecap). Medial and lateral plicae are also often connected to the Fat Pad and to a Ligamentum Mucosum, and often inflammation can be found in multiple connected plicae at the same time.

No-one knows why it is that a plica (which will have been there from birth) actually becomes inflamed and symptomatic. However, plica syndrome tends to occur in people in their 20s or 30s – and specifically in people who do a lot of running (or sometimes long-distance cycling). People with plica syndrome tend to find that using the cross-trainer or swimming with front crawl legs is actually absolutely fine – this is because there is no repetitive bending of the knee joint with these activities, and therefore the plica is not actually rubbing against the edges of the inside of the knee and becoming inflamed.


Investigation/Imaging

Plica Syndrome is difficult to diagnose from imaging. Plicae don’t show up at all on X-rays. Although a plica can be seen on an MRI scan, an MRI will not tell you whether any plica that might show up is actually symptomatic or whether it might be just coincidental. MRI is, however, extremely useful for excluding other potential pathology (such as meniscal tears or articular cartilage damage) that can mimic the symptoms of Plica Syndrome. The diagnosis of Plica Syndrome is, to some extent, a diagnosis of exclusion (one has to exclude all the other various pathologies that can potentially cause similar symptoms).


Treatment

Plica Syndrome is not in any way dangerous or damaging at all. However, it can be very annoying and it can prevent some people from being able to exercise properly. If the symptoms from Plica Syndrome are severe enough then specific treatment might be justified.

Physiotherapy can help with general biomechanical and postural correction and with improving core strength and neuromuscular control. However, physiotherapy cannot actually directly cure Plica Syndrome.

Steroid injections can be given into the knee, and these act as very powerful anti-inflammatories – like taking a massive dose of Nurofen all in one spot. This can reduce inflammation and therefore symptoms. However, a steroid injection simply masks a patient’s symptoms in their knee and will not ‘cure’ the underlying problem.  The worry with steroid injections is that they do not really help clarify or prove the exact diagnosis of the underlying pathology, and there can be a risk of any mechanical damage in the knee actually getting worse whilst the symptoms are being masked by a steroid injection, and the underlying problem can then come back worse and be more of a problem once the effect of the steroid has worn off, after a couple of months.  However, if the knee has been carefully checked and if there are no specific conerns, then a steroid injection is quick, easy, relatively cheap and pretty low risk, and it is therefore a reasonable option, even it is does only give temporary symptomatic relief (which may, potentially, be all that is required).

The best and only proper way to cure Plica Syndrome is to surgically excise (trim) the plica through keyhole surgery (knee arthroscopy).

   

CLICK HERE for more information about plica syndrome and arthroscopic plica excision.