Meniscal tears and the arthritic knee

Dr David Colvin workers compensation

02/11/2018 Dr. David Colvin, trained in orthopaedic surgery in Perth. David's specialty is knee and shoulder surgery and sports injuries.
The meniscus is the rubber cartilage in the knee. We see meniscal tearing or torn cartilages in the knee in two settings.

Firstly, everyone has heard about the young footy player who has a twisting injury, keyhole surgery to tidy up the torn cartilage and he is back on the field in a month or so.  That is a tear in a normal cartilage as a result of excessive load or twisting force. 

The second context in which we see meniscal tearing is what we refer to as a “degenerative” tear.  In this setting, there are often arthritic changes in the knee.  At the same time that the arthritis is evolving, the rubber cartilage is degenerating or “perishing”.  Just like rubber, the meniscus can harden and tear with age.  This happens at different ages but can start as early as your mid thirties.  In other people it can occur in their seventies.  Some people just inherit more durable rubber cartilages than others.

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A degenerative meniscal tear can look like crab meat, a piece of rubber that has been hit with a hammer repeatedly.  Tears of this nature cannot be repaired.  The question is should they be removed?

There has been much discussion in the popular press of late about the role of arthroscopic surgery for arthritic knee joints.  There is now compelling medical evidence to say that keyhole surgery or a “clean up” for an arthritic knee has no benefit in the medium to long term and is not recommended. 

The decision making is more difficult when there is arthritis and a degenerative meniscal tear.  It is even more complex in the context of a work related injury to the knee. 

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The meniscal tear may have been caused by the work injury, or a pre-existing tear may have been made worse by the work injury and thus become painful.  Alternatively, the meniscal tear may be entirely pre-existing and the work injury has caused arthritis in the knee to become painful when it was not painful previously.  Investigations such as MRI cannot answer these questions.

How do we decide who should have an arthroscopy?

  • Conventional advice is that if there is a catching sensation or locking of the knee, then this could be caused by a torn cartilage flicking in and out of the knee and there is potential for this to be improved by surgery.
  • The younger the patient, the more open we are to considering keyhole surgery.
  • If the patient is unable to do their occupation or to continue with their current symptoms, then it is a reasonable consideration.

What have we got to lose?

  • No surgery is without its risks, but for a young patient undergoing an arthroscopy, the risks of anaesthesia, infection and deep vein thrombosis are all very low. 
  • The catching sensations can be caused by roughened arthritic surfaces.  There is no guarantee that surgery for a torn cartilage will relieve a catching or locking sensation in the knee.
  • The arthritis could get worse.  Generally speaking, we do not think this is a result of the surgery provided that the clean up is done very cautiously with preservation of all good tissue remaining.  However, the knee may have become painful because the arthritis is deteriorating and arthritis can deteriorate rapidly in some cases.  Up to one in ten patients can be worse six months later.  This is likely to be due to the deterioration of the arthritis rather than the arthroscopy.

In summary, it may be reasonable to consider arthroscopic surgery for a meniscal tear in the presence of some arthritis, particularly if there is catching or locking. The success rate for arthroscopy in this setting is obviously not universal but alternative treatment such as joint replacement are major surgery and not to be undertaken lightly.  Arthroscopy is not appropriate if there is bone on bone severe arthritis. 

The other important point is that arthroscopy for an arthritic knee should be considered part of the overall treatment plan.  The non-operative treatment is just as important and should be happening at the same time. 

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