Ligament Injury

Ligaments are strong bands of tissue that act like a tight rope, holding the knee joint together.  The knee joint is intrinsically unstable, in the form of a complex hinge mechanism, which is stabilised by a combination of ligaments and muscle action around the joint.  Whereas the muscle work dynamically to stabilise the knee when walking and running, the ligaments are passive constraints on the knee joint, preventing abnormal movement.  There are two pairs of ligaments which are particularly important. 

Firstly, the collateral ligaments (medial – MCL, and lateral – LCL) which are located on the inner and outer sides of the knee.  Secondly, the cruciate ligaments (anterior – ACL, and posterior – PCL), which cross the centre of the knee joint.  Ligaments are commonly injured in sport by force applied to the knee when twisting or falling, however a heavy fall or a collision is not always required to damage a ligament.  Anyone who saw Michael Owen injuring his knee in the World Cup would be struck by the relatively innocuous incident which causes ACL to ruptured.

The Anterior Cruciate Ligament ( ACL) passes obliquely across the centre of the knee

  • ACL injuries.  The ACL is located in the centre of the knee and controls forward movements of the tibia.  This is most commonly injured by twisting injuries and the ligament can often be felt to “pop” as it tears.  Blood vessels in the ligament will bleed, so typically the knee becomes very swollen within 24 hours as the joint fills with blood.  Unfortunately, the ACL has no capacity to heal spontaneously. When the ligament is torn the knee will develop a characteristic pattern of instability where the tibia can move forwards abnormally in relation to the femur (termed “anterior drawer”).  The knee will be unstable in certain conditions, particularly during activities which require sudden changes in direction, such as side stepping or swerving.   These activities place abnormal stresses on the knee which are normally resisted by the anterior cruciate ligament and when it is torn there is no constraint to these movements and the knee will give way.   Very often, when the anterior cruciate ligament is damagedthe initial discomfort settles relatively quickly and a return to sport may be attempted.   When running and turning suddenly the knee will buckle or give way and may potentially cause further damage in the knee joint to the menisci and the joint surfaces. Recurrent giving way of this type is very damaging to the knee joint and almost certainly is a factor which predisposes to osteoarthritis. 

It has been recognised for many years that damage to the anterior cruciate ligament is a major impediment for individuals who wish to return to an active sporting life.   Over the last 20 years a great deal of work as been undertaken in developing the operation of anterior cruciate ligament reconstruction, using the technique of keyhole surgery.  The ligament will not heal spontaneously and the only effective option is to replace the damaged ligament with a tissue graft, using tendons usually taken from the same knee. The tendon grafts most commonly used are either the hamstring tendons (gracilis and semitendinosus) or part of the patella tendon (termed a “BTB – bone/tendon/bone graft”) from the front of the knee.  The operation involves using the arthroscope to remove the remnant of the anterior cruciate ligament and to prepare tunnels in the bones on both sides of the knee joint, which allow the graft to be inserted very accurately and fixed firmly in place. This allows immediate rehabilitation by exercising the knee, which is essential for a rapid and uneventful recovery.

Physiotherapy is central to the treatment of all knee ligament injuries, ACL reconstruction in particular. A progressive exercise programme is used to encourage walking and knee bending exercises, as well as strengthening exercises for the quadriceps and hamstring muscles.  Balancing exercises to re-establish coordination (termed “proprioception”) are also an important part of the rehabilitation process.  The physiotherapist will guide the patient through the different stages of the rehabilitation programme, aiming for a return to pre-injury activities.  The rate of recovery is very individual but, on average, someone in a sedentary occupation can expect to return to work within two to three weeks, whereas someone in a physically demanding occupation may take as long as six months.  With regard to sport, non-contact sport is usually possible after six months but a return to contact/collision sports (such as football and rugby) may take between nine to 12 months.

A PCL injury. Note the posterior displacement of  the tibia on the femur.

  • PCL injuries.  Injuries to the posterior cruciate ligament are less common and are often caused by a direct blow to the front of a bent knee, such as when falling onto hard ground or in road traffic accidents when the knee is struck by the dashboard of the car.  The PCL function is to resist backwards displacement of the tibia in relation to the femur.  In general, PCL injuries are better tolerated than anterior cruciate ligament injuries, in terms of symptoms of instability and giving way, which are relatively uncommon following PCL injuries.  The PCL is a very strong ligament and it can be stretched to varying degrees without rupturing completely. 

Isolated injuries to the PCL are usually treated non-surgically by rehabilitation of the quadriceps muscles, usually with a satisfactory outcome.  In more severe, high energy injuries, the PCL may be ruptured completely, very often in combination with injuries to other knee ligaments.  In this situation, surgical reconstruction with a tendon graft, similar to the ACL reconstruction procedure, may be required.

The Medial Collateral Ligament (MCL)

  • Medical collateral ligament (MCL).  The MCL is a strong band of tissue, which runs across the inner (medial) side of the knee and stabilises the knee when forces are applied to the outer side of the knee joint.  Injuries to the MCL are commonly seen in contact sports in activities such as skiing.  The MCL is very strong and does not rupture completely.  Injuries are divided into three grades.  In Grade I injuries, the ligament is sprained but is structurally intact.  In Grade II injuries, there is a partial tear of the ligament but the bulk of the ligament is still structurally intact.  In Grade III injuries, the ligament is torn completely. 

Most MCL injuries do not require an operation but will be treated slightly differently, depending on the grading of the tear.  Grade I injuries will require ice, early movement and exercise to keep muscles strong.  Recovery of knee function is usually quite rapid and a return to sport within four to six weeks is expected.  In Grade II injuries, a temporary period of immobilisation in a splint or range of movement brace will be helpful, but this can be removed relatively soon, as pain settles, Exercises can be commenced to strengthen thigh muscles and re-establish knee movement.  A return to sport takes somewhere between six to eight weeks.  In Grade III injuries, the knee will be braced by a gradual increase in range of movement over a period of six to eight weeks.  Initially, weight bearing will be protected by using crutches.  On removal of the brace, physiotherapy is required to re-establish knee movement.  Recovery takes a longer; a period of three to four months is not unusual. 

MCL injuries can be complicated by a combined injury with the anterior cruciate ligament.  This is a much more complex combination, often seen in skiing injuries. The accepted treatment for this combined ligament injury is to brace the knee for four to six weeks to allow initial healing of the MCL before proceeding with reconstruction of the anterior cruciate ligament using a tendon graft.  After surgery, further protection of the repair will be required for another four to six weeks.

The Lateral Collateral Ligament (LCL)

  • Lateral collateral ligament.  The LCL is a cord-like structure on the outer side of the knee, which stretches between the head of the fibula and the outer side of the femur.  The LCL will be damaged by blows to the inner aspect of the knee.  These are usually high energy injuries, often combined with damage to other ligaments, particularly the ACL and PCL.  The LCL usually pulls off from its attachment to the head of the fibula or side of the femur and early surgical repair of this injury is recommended.

RWN’s view

Most of the debate surrounding knee ligament injuries focuses on the best methods of treatment for anterior cruciate ligament injuries.  A further topic that is often debated is whether all patients who have suffered anterior cruciate ligaments should be offered an operation to reconstruct the ligament.  In my view, not everyone who ruptures their anterior cruciate ligament requires an operation.  In a relatively sedentary individual who may damage the anterior cruciate ligament on an annual skiing holiday, the injury may be very effectively treated by rehabilitation alone.  It is important to discuss the expectations of the invidual to determine what type of activities they enjoy in order to enjoy the potential risk of further problems with instability and recurrent giving way of the knee.  Although age may be a factor (only because we tend to become relatively less active and change the nature of our sporting activities as we get older), the principal decision should be made on the type of activities enjoyed by the individual and whether there will be a risk of knee instability when they have recovered from the injury and returned to their sport.  These issues should be discussed in detail and the individual should be counselled as to whether knee ligament surgery is advisable. 

The second topic which often arises is when ‘should the operation be performed?’  There has been a great deal of debate as to whether early repair of the anterior cruciate ligament runs a risk of causing scar tissue to develop within the knee (arthrofibrosis).  Several studies have looked at this subject and have concluded that there is no significant risk in performing surgery early, however there does not appear to be any major advantage either.

Technically, surgery is easier if the initial swelling is allowed to subside and exercises have re-established knee movement.  I usually recommend that the anterior cruciate ligament can be reconstructed between two to four weeks following an acute injury, with a satisfactory outcome.

Thirdly, there is a great deal of debate about ‘which is the best graft to use to reconstruct the anterior cruciate ligament?’ This is very much a “horses for courses” situation, where an appropriate graft should be selected, depending on the nature of the knee injury and the individual.  I use both hamstring and patella tendon grafts, as well as tendon transplant grafts (allografts) in certain circumstances.  I feel particularly strongly that combined injuries of the anterior cruciate ligament and medial collateral ligament should be treated by either a patella tendon graft, a tendon graft taken from the opposite leg, or possibly an allograft.  There is no convincing evidence that one particular type of graft is better than another and in genera either hamstring tendon grafts or patella tendon grafts can be considered to function equally well in most cases.

Finally,’how long should you wait before returning to work and sport?’  I defer to the expert physiotherapist who cares for the patient after surgery.  They are very good at assessing my patients, treating them individually to determine how well they are progressing through the different stages of the rehabilitation programme.  Rather than using rather arbitrary time intervals, the modern approach to rehabilitation following anterior cruciate ligament reconstruction uses specific objectives in the rehabilitation programme. When the individual can achieve one level of objectives they can then move on to the next level, progressing towards normal knee function.  By seeing how well the individual patient achieves these objectives, more informed advice can be given on when the individual can return to work and sport. 

In general terms, office based work should be possible within two weeks of surgery but strenuous manual work should be considered in similar terms to sport and will take about six months before a staged return to work should be considered. In sport, for non-contact sports, approximately six months is a reasonable objective, whereas in contact sports, such as football and rugby, nine to 12 months is more realistic.