ACL INJURY

motion is preserved but with more stress on the medial meniscus. In time this attrition results in a medial meniscal tear. With the loss of function of this structure the medial joint surfaces are overloaded resulting in medial osteoarthritis, and a sudden worsening in instability symptoms.

There are a number of good studies which show how long term ACL deficiency is associated with premature osteoarthritis from the accumulation of repeated chondral injuries and meniscal tears. There is now good evidence that surgical reconstruction of the ACL reduces the incidence of later meniscal tears.

Unfortunately there are a few studies which suggested ACL reconstruction surgery caused increased risk of osteoarthritis. These papers usually have serious flaws in methodology. For example they often compare the results of groups determined by patient choice - those who are relatively sedentary who decide not to have surgery and those who are usually more active who do have surgery but, of course, are also more likely to have future unrelated knee injury from sports participation. In addition these papers are now rather historic since the patients had operations which would now be thought of as crude. It is however correct to note that badly performed surgery can be devastating to a joint and far worse than non-surgical treatment.

I do however emphasise to all my non-sporting patients that ACL deficiency does not equate to an operation. If they do opt for non-surgical treatment, then I warn them that they must not ignore episodes of giving way of the knee, and furthermore even a lack of trust equates to less severe, but significant, instability. If this transpires then I recommend these patients have surgical reconstruction before the situation is irreversible. It is the recurrent minor subluxations, or single episodes of major giving way that do the damage.

NON-SURGICAL MANAGEMENT OF ACL TEARS This relies on enhancement of neuromuscular control of the knee by training for strength, control and agility, and bracing. Whilst it is impossible to restore the proprioceptive feedback provided by the nerves of the ACL itself, overall proprioception can be maximised by making the best use of what is left.

Braces are frequently used by patients for sports activities. They function in two ways. Firstly they provide a passive restraint to abnormal motion. However, whilst this concept is attractive and logical, the efficacy of braces to achieve this is rather less than the manufacturers would like to acknowledge. Braces are probably reasonable restraints to varus/valgus, but less so against antero-posterior movements of the tibia/femur and very poor in restricting rotational movements. Grasp your forearm or leg and the bones can still easily be rotated regardless of how hard your grip is. Since instability is felt during abnormal rotatory subluxation ie. a pivot shift, braces are less effective than hoped. However they have a second way of enhancing stability, by compressing the soft tissues and skin about the knee, the motor centres of the brain receive more proprioceptive input which can aid 'fine-tuning' of muscular control. This is the mode whereby flimsy knee supports, such as 'tubigrip' can help the individual.

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There was a time when knee braces were worn prophylactically, especially in American football, but there was no evidence that ACL rupture rates reduced.

Physiotherapy obviously plays a key role in non-surgical manage- ment of ACL deficiency. It emphasises step-wise progression of building strength, stamina, and agility. Muscle needs to be strong, concentrically and eccentrically, and quick-firing. Whilst the 'ballis- tic' contraction of the hamstrings is very desirable it is only a detail in the programme. Of course, trunk as well as limb control/strength should be part of the training. Since 'agility', which requires learn- ing motor skills and various aspects of neuromuscular control as well as proprioceptive sense, is the desired end result and since patients actually understand the word, I prefer the term to ‘propri- oceptive training’.

Unfortunately when the initial recovery is good the patient needs to realise that the process will often need repeating if they are to remain without symptoms. If the patient is genuinely asymptomatic then they do not need surgery. However, since I believe that overall, the risk of leaving knees ACL deficient is far greater than the risks of well carried out surgery, I emphasise to those treated successfully non-surgically that they represent the exception rather than norm. Therefore they need to acknowledge that they are vulnerable.

THE AUTHOR

Mr Andy Williams FRCS (Orth) is a consultant orthopaedic surgeon at The Chelsea and Westminster Hospital, London. He qualified from King's College Hospital, London in 1987 and undertook his orthopaedic training at The Royal National Orthopaedic Hospital, Stanmore followed by a year's Fellowship in Brisbane, Australia which is where his experience with sports-related surgery began. On return to the UK in 1997 he became senior lecturer/honorary consultant at Royal National Orthopaedic Hospital, Stanmore and in January 2000 he moved to his current post. His elective practice is now almost exclusively knee surgery with around 75% on soft tissue knee surgery specifically. He undertakes around 200 ACL reconstructions per year and a multi-ligament reconstruction every 3-4 weeks. This latter work represents one of the world's largest experiences. Knee replacement makes up the remainder. He is currently the primary knee surgeon for most of the professional sports teams in London, particularly in rugby and football. He has published widely on the study of knee motion employing weight-bearing, 'dynamic' MRI. Other research interests are in the fields of tissue engineering, and knee ligament injuries. He is a lead editor of the latest edition of Gray's Anatomy published in December 2004 and he was awarded The Hunterian Professorship by The Royal College of Surgeons of England for 2005-2006. Until recently he was on the executive of The British Association for Surgery of The Knee.

The next article is written by the same author and looks specifi- cally at surgical reconstruction of an ACL deficient knee.

RELEVANT SPORTEX READING ‘The Effect of Gender on Lower Limb Musculotendinous Stiffness and implications for ACL injury’. Bryant A and Hohmann E. sportEX medicine 2007;32(Apr):23-26

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