Meniscal Injuries

Introduction

The meniscus, or footballer’s cartilage, is the protective shim between the femur and tibia. It is classically injured in a weight bearing twisting type mechanism. 

The main function of the meniscus is to protect the articulating surfaces of the bone by distributing the load across the joint.  The lateral meniscus is the most important as it takes 70% of the weight that goes through the lateral half of the joint.  Removal of this structure therefore results in a dramatic increase in load through the joint and early failure of the articular surface. 

The articular cartilage is the smooth glistening white surface that is virtually frictionless.  Damage to this surface results in increased friction and wear on the joint.  This leads to further damage and degeneration – osteoarthritis. 

Diagnosis of a torn meniscus

A full house of symptoms and signs for a diagnosis of a torn meniscus are as follows:

• History of weight bearing twisting injury.
• Effusion in the knee joint.
• Specific joint line tenderness.

1.    Injury Mechanism.

Injury to the meniscus can occur in virtually all age groups and the underlying theme is a twisting injury on the weight-bearing knee.  In the younger active individual tears tend to be classified as traumatic in pattern where there is a clean tear through a healthy meniscus.  The opposite pattern is a “degenerate” style tear with much more of an irregular crushed appearance.  Such tears often exist in the generally degenerate knee.

2.    Effusion.

The torn meniscus irritates the joint generating an increase in synovial fluid forming an effusion.  This is seen as a swelling in the medial, lateral and supra patella area.  The patient may describe this as ballooning of the joint or loss of the normal divot or dent seen on the medial aspect of the patella.  With time the swelling will settle only to recur after a minor twisting injury.  Patients may therefore avoid going back to activity for fear of re-inflaming the knee.

3.    Joint line tenderness.

This is very specific to a meniscal tear and there is a pinpoint location on the medial or lateral side associated with the relevant injury (see diagram) To find this area the joint line has to be identified and this is best found by initially palpating the soft spot on either side of the patella tendon and following the soft line posteriorly from that point between the femur and the tibia.  It is best felt by firmly applying the pulp of two fingers to the joint line and slightly rubbing in a superior / inferior direction to generate point tenderness.  This can be compared to the other knee if there is doubt as to whether there is genuine tenderness compared to normal.  The tender point on the medial side is slightly more posterior than on the lateral side.

 




Lateral meniscal tears may be associated with a swelling or cyst formation which is a fullness felt on the joint line overlying the mid part of the lateral meniscus.

The knee joint may often need to be supported with the other hand in order to generate sufficient pressure to elucidate the tenderness. 

Symptoms

The main symptom of a torn meniscus is pain and this is generally well localised to the edge of the knee joint.  If there is significant swelling in the joint then this will manifest as a sensation of stiffness and tightness on bending the knee. 

A further symptom is intermittent locking or giving way as the torn fragment of meniscus catches.  By a locking we traditionally mean that the knee will not go fully straight as the torn fragment blocks the space between femur and tibia preventing full extension.

Treatment Options and Timing

Not all meniscal tears need surgical treatment and acute tears need time to be allowed to heal on their own.  In general a tear that settles down and does not cause swelling in the knee does not need operative treatment if it is not causing significant pain or interference with function. 

In the acute setting some tears can heal and if this is to happen then it is usually clear by six weeks whether the knee is going to settle or not.

Locked knees however are different and should be referred for early hospital treatment.  In this situation a piece of the torn cartilage is blocking the knee from going out fully straight and this will not clear itself.  Delayed treatment in this situation results in a significant increase in rehabilitation time and makes it very difficult to finally get the knee out straight.  The knee of course may also be blocked by a fragment of joint surface or the torn anterior cruciate ligament stump. 

Often, symptoms from a meniscal tear are related to activity and are exacerbated by sport or catching the foot on the ground, sharply twisting the knee.  Patients will often describe that their knee has settled but this may be because they have generally stopped the actions that precipitate the pain. 



Surgical Treatment

The main stay of surgical treatment for a torn meniscus that is causing symptoms of pain and swelling is arthroscopic resection of the torn fragment.  This is usually a day case procedure with the post operative recovery taking one week to return to desk work and two weeks to manual work.  Sport can be commenced after that stage.

Repair of the torn fragment, stitching it back into its normal place, is a possibility but only a small proportion of tears are of the type that can be treated by such technique.  This is because the meniscus does not have its own blood supply apart from the peripheral part and tears are uncommon in this area.  If repair is undertaken then a strict rehabilitation programme has to be followed limiting knee bend for the first two to three months.

Meniscal transplantation and the use of synthetic scaffolds are new options for the management of patients who are suffering after resection of whole or part of their meniscus.

Meniscal Scaffolds: Regenerating the shock absorbers in the knee

The menisci of the knee make the sockets for the thigh bone to rotate in and they provide the shock absorber for impact loads. If a substantial amount is removed after injury then this can result in early wearing of the joint surfaces. Complete loss of the meniscus usually results in early arthritis developing within 10 – 15 years.

The Meniscal Scaffold implant is a new device designed to rebuild the meniscus after part of it has been removed. This procedure of partial meniscectomy is very common and is usually successful in relieving pain. However a small proportion of patients will develop persistent pain felt in the side of the knee due to the lack of the normal thickness of the meniscus.

The implant acts as a scaffold for new tissue to grow into and regenerate the healthy cushion. Early published results show it to be successful in relieving pain after meniscectomy. However the long term benefit of reducing the severity of later arthritis in the knee is not yet fully clear as the technology has not been around long enough.

The brand of implant that we currently use to regenerate the meniscus when part of it has been removed is the ACTIFIT, supplied by Orteq.  It was developed in Belgium and is made from a polyurethane polymer.  Laboratory studies indicate the scaffold may still be present 5 years after implantation giving the body longer time to form a new natural regenerated meniscus.

The ACTIFIT Operation and Rehabilitation

The implant is inserted at key-hole arthroscopic surgery which is usually a day case procedure.  The incision to get the implant into the joint is about 2 – 3 cm long.
Rehabilitation after surgery naturally has to be slow as the body has to grow tissue into the scaffold and this is a slow process. Full weight on the leg is allowed at 8 – 10 weeks and the specific rehabilitation program is tailored to each patient depending on the state of the knee surfaces and the amount of new meniscus inserted. Biopsy studies looking at the new tissue under the microscope have shown that the new tissue is fairly strong by 12 months. Impact sport is therefore not allowed for the first 12 months.
For more detailed information see www.orteq.co.uk

Meniscal Allograft Transplantation: for when the whole meniscus has been removed.

If the whole meniscus has been removed then the scaffold synthetic substitute will not suffice and a meniscal transplantation using a donor graft is indicated. We have now performed over 140 meniscal transplants.

Meniscal Transplantation involves implanting a donor graft (allograft) supplied from a tissue bank in the UK or from the USA. The remnants of the old meniscus are trimmed back to make a fresh bed for the new meniscus which is then inserted by keyhole surgery (arthroscopy) and stitched to the original bed. It then heals to the bed on the side capsule of the knee joint so that it can provide cushioning for the smooth articulating surfaces.

Grafts are donated rather like heart transplant donors and are very carefully prepared by the regulated tissue banks to ensure that the tissue is as free of disease risk as is possible. This process has been highly regulated and advances in testing for infections such as Hepatitis and HIV has meant that the risk of contracting severe infections through the grafting operation are now very small. Though difficult to fully quantify, the risk is less than that from a blood transfusion.  Grafts are decontaminated and then cryopreserved until required.

Indications for Meniscal transplantation surgery

The procedure is indicated when there is no effective rim of meniscus remaining to support the joint surfaces. This occurs when there has been a large tear and when it was not possible for the surgeon to salvage the meniscus by repairing it. Not everyone needs a transplant but if there is progressive pain and symptoms limiting activity then the procedure may be indicated.

There is often a feeling that it is necessary to always replace the meniscus if it is removed, based on the argument that it will prevent or delay the onset of later arthritis. This is a difficult issue, but because the rehabilitation period is long and because the operation is not without risks, meniscal transplantation is usually only performed when symptoms of pain on activity begin to cause interference with your quality of life.

The quality of the result of the operation is a key factor in deciding the indications as the replacement tissue is, after all, a donor graft that may not be as strong as the original and it takes time for it to fully integrate into the knee. Having invested a year of time in getting it right after surgery the thought of going back to full contact sports such as football and rugby could be considered ill-advised!

Recent research looking at the outcome by the leading surgeons in the US and in Europe would indicate that at 10 – 13 years approximately 70% of patients still have good function and have not had further surgery. Most have been able to do light sports. The occasional professional athlete may report being able to get back to high level but it should be remembered that professional athletes may have different goals.
 
Following surgery the rehabilitation process involves using a knee brace for the first 6 weeks while the new meniscus heals in place but return to any form of sport is not before 6 months. Impact pivoting sports are probably best avoided.

Additional Procedures

In over 50% of our cases the transplantation operation is performed in conjunction with other procedures and depending on this the rehabilitation regime may change. Additional procedures may include

• Surgical procedures to repair the joint surface such as microfracture or autologous chondrocyte implantation
• If the joint is failing because the leg is out of alignment (bow-legged or knock-kneed) then osteotomy or realignment corrective surgery is needed.
• If the knee is unstable due to a ligament injury then transplantation can be combined with anterior cruciate or posterior cruciate ligament reconstruction.

Overall meniscal transplant is an exciting option for the damaged knee allowing for substantial improvement in the quality of your life. Though a challenging procedure with a long rehabilitation program, the technique alone or when combined with other surgery, provides a realistic biological option for knees, hopefully avoiding, or at least delaying, the need for metal and plastic knee replacement operations.