Sprains of the medial collateral ligament (MCL) of the knee

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Introduction

Football carries a high risk of knee injuries due to the essential emphasis placed on the lower limb (Dick et al, 2007) with sprains of the medial collateral ligament (MCL) of the knee commonplace (Le Gall et al, 2006).   

Injuries to the MCL, which limits the excess movement of the knee in an inwards, or medial direction, are frequently sustained and usually result in an average 6 – 8 weeks absence from the sport based on the recovery time for a typical Grade 2 ligamentous sprain.

Previous research has shown that the MCL is the most commonly injured structured in the knee (Wijdicks et al, 2010); with MCL injuries in football resulting from an excessive valgus force which usually occurs through making direct contact with an opponent.   

For clarification, a valgus force is the description given to a movement that results in the medial aspect of the knee joint being forced inwardly; leading to increased stress being placed on the supporting structures.  

Basic anatomy

The knee is synovial hinge joint comprising of the articulation of the bones of the tibia and femur, lined with articular cartilage and principally stabilised externally by strong collateral ligaments reinforced with a capsule and internally by the anterior and posterior cruciate ligaments. 

The anterior cruciate ligament (ACL) lies deep within the knee and connects the femur to the tibia. Its major mechanical function is to prevent excessive forward movement of the shin with the knee in various degrees of flexion (Liu-Ambrose, 2003.) 

Anatomically, the ACL runs within the knee from the medial surface of the tibial plateau and extends upwards, backwards and laterally to insert on the lower aspect of the femur. 

The cruciate ligaments are static stabilisers that play an intricate part in adding stability to the knee throughout its full range of movement (Logterman et al, 2018) in conjunction with the medial and lateral collateral ligaments of the knee which provide stability in a side-to-side direction.  

The MCL provides the primary stability between the femur and tibia on the medial aspect of the knee (Marchant et al, 2011), while the lateral aspect of the knee is restrained by the lateral collateral ligament (LCL) which runs from the femur to the head of the fibula bone.

Dynamic stabilisation of the knee comes from the supporting musculature of which, amongst others, includes the three hamstring muscles posteriorly.  These  are counterbalanced by the quadriceps muscle group at the front of the thigh within which the patella bone or kneecap is sited. 

MCL injuries can occur in isolation or combination with simultaneous injuries to other structures of the knee and are known to accompany injuries to the Anterior Cruciate Ligament (ACL), the medial meniscus, or as a combination involving all three structures.   

When the MCL is injured in conjunction with the ACL and medial meniscus, this is known as O’Donoghue’s Triad; a complex injury that results in a lengthy absence from the sport and almost always involves surgery; usually to the ACL.   

Injury mechanics

The most frequent cause of isolated MCL injury in football is through direct contact with an opponent, usually in the tackle; but these can also occur via non-contact mechanisms if the knee is twisted while running.  

One common mechanism of MCL injury occurs when a player is tackled from the side.  If the blow from the tackle is received on the outside of the knee, the limb will give way and the knee will be forced inwards into a position where the ligament is stretched or torn.   

A typical ‘block tackle’ made to the inside of the foot has the same effect when the force of the tackle damages the knee ligaments as the joint is forced past its normal range of movement. 

As a strong, thick, flat band of connective tissue, when the MCL tears, it tears under the generally-accepted grading system where injuries and classified by severity.  

Grade 1 injuries are minor sprains with damage limited to only a few fibres of the ligament.     A Grade 2 injury involves considerably more than a few ligamentous fibres and is considered to be a ‘moderate’ injury; while a Grade 3 tear is a complete rupture.  

It has to be said, though, that there is an emerging school of thought which suggests that these ‘traditional’ classifications are now less relevant in modern-day sports medicine and should be replaced by a more accurate system (Mueller-Wohlfart et al, 2012).   

Discussing a Grade 2 sprain that in reality just exceeds a minor Grade 1 injury leaves ample scope for variation in its interpretation.  At the other end of the scale, a higher range Grade 2 sprain can effectively border on a grade 3 rupture barring a few intact fibres!    

In MCL injuries, the most tender area is localised to the inside aspect of the knee, corresponding with the actual joint-line where the ligament crosses the junction where the medial meniscus is attached.  

If the injury is severe enough, this area might be warm to the touch. It will certainly be painful; so digging your fingers in and asking ‘does this hurt?’ is not a good idea!    

The mechanics of the injury will indicate an MCL sprain anyway; but the important part now is to assess how much damage has been done to the knee and whether there are any other structures involved.   

Attempting to take any bodyweight through the joint will only result in the feeling that the knee will collapse.  Any sideward movement such as applying valgus stress will increase pain and also potentially worsen the injury during the acute stage.  

MCL injuries should be seen by a doctor or physiotherapist who may initiate deeper investigations if appropriate to rule out associated injuries to other structures such as to the meniscus, cruciate ligaments, accompanying soft-tissues or even bony injury.   

Correct management in the initial stages of injury sets the tone for the whole rehab period.   A hinged knee brace and crutches are usually the order of the day immediately following knee ligamentous injuries.      

This will assist with early management, reduction of pain, and to support the injured structure(s).   However, the main purpose of the hinged brace is to protect against any sideways movements until the damaged tissues start to heal.     

The most effective method of treatment is to partially immobilise the knee in a hinged brace fitted with metal stabilisers on either side to prevent medial and lateral movement as soon as possible after the injury has occurred.     

Hinged braces are easily sourced on most sports medical suppliers’ websites but will normally be routinely issued at the time of the initial appointment with a clinician. 

If we happen to be dealing with an unstable knee immediately post-injury then the player must be seen by a physician with the minimum delay.   

The importance of using a hinged brace  
 

Ligamentous tissues are at their most vulnerable in the immediate period following the injury; and if left unsupported will heal in a less than ideal position.  

To prevent acute MCL sprains leading to instability, early injury management should focus on immobilising the knee in such a way that the ligament is under minimal stress. 

Since ligamentous structures need to be tight and strong to support the joint they are meant to protect; if left unchecked these will stretch and heal in a looser position than is required, leading to an unstable or wobbly knee in the future. 

This happens because healing tissue is like soft plaster; and the more it is disturbed before it is allowed to set properly, the less strong the result will be. This can mean that a greater risk of incomplete healing could take place, potentially leading to recurrence or chronic instability in the future. 

Although immobilisation techniques may vary (Sommerfeldt et al, 2015) use of a hinged brace will allow for the safe movements of bending and straightening the knee to take place whilst stabilising the inwards (valgus) movements that stress the MCL.  

From a rehabilitation aspect, it’s vitally important to keep the knee moving through the ranges not directly affected by the MCL in order not to lose any natural movements that are unaffected by the injury.  

Gentle bending and straightening won’t place much stress on the collateral ligaments anyway since the movements to avoid are those in a sideward direction.  

However, it is important to remember that if swelling is present then this can restrict available movement ranges. 

Once the healing process has begun and associated injuries to the meniscus and ACL etc. have been excluded, physical therapy involving strengthening exercises for the knee as a whole can then be initiated.  

Discussion:  Surgical v non-operative management of MCL injuries 

There has been constant debate throughout the years over the benefits of surgical v non-operative management for isolated MCL injuries.   

Instability of the knee arising from an MCL sprain is often the biggest risk and occurs when the ligaments that stabilise the joint have been stretched or torn, and are no longer able to support the joint. 

Over time, chronic laxity develops and the knee becomes inherently unstable if untreated.  Such laxity can lead to the knee feeling “loose and wobbly”; often with an accompanying sensation that the knee is going to “give way”.  

If severe enough, initial injuries to the MCL can also result in instability if left unaddressed in cases where the injury is classified as either a Grade 3 sprain or a higher-end Grade 2 injury.  

In these cases, many surgeons believe that the best results in MCL rehabilitation are gained through the surgical reconstruction of the ligament.  Where repeated injuries have led to chronic laxity over time, several consultants prefer to follow the operative route while others disagree.
 

Phisitkul et al (2006) discussed the potential for both options and concluded that although surgical treatment may have a role to play in many cases, most medial-sided knee injuries are better treated non-operatively; particularly in cases of minor Grade 1 and lower Grade 2 ligamentous sprains. 

The general feeling is that rest, early movements and controlled activity during the early period immediately post-injury are the methods of treatment favoured by most orthopaedic surgeons and sports medicine professionals.  

In many cases, though, it is the immediate treatment and management of injury that leads to a successful rehabilitation period and ultimately a return to play. This will vary depending on the severity and nature of the injury. 

In football, though it's not just about the medical management of injuries, there are the components of the game to consider also. Returning to play after a long period out of action as a result of an injury needs to be managed correctly in addition to following the medical advice given by the physician or therapist. 

Return to the team is dependent on the strength of the injured knee matching that of the non-injured side, ensuring that the injured knee has the same flexibility as the non-injured side, and finally is pain-free without showing any adverse reaction to physical exercise. 

Of course, it's also essential to address the football aspects of the recovery process. Players coming back from injury need to be able to complete all the things required during the game such as running, twisting, turning, kicking, jumping and sprinting etc., before being considered for a return to the team. 

Attempting to go straight back into the team without first of all ensuring that your player can meet all the requirements of the game is only asking for trouble and is likely to lead to repeat or recurrent injury.   
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