Sandyford, Dublin 18
Sports Injuries of the Knee
Introduction
The knee is a complex joint with many planes of movement, rather than being a simple hinge. It is susceptible to sports injuries, usually through twisting or by direct contact.
The articular surfaces of the knee (where the bones come into contact with one another) are covered with hyaline cartilage. This is a unique tissue to joints which allows a low friction environment coupled with durability. Also, within the knee are two meniscal cartilages, one on the inside aspect (medial) and one on the outside (lateral). These crescent shaped structures are essential components of the knee acting to distribute load, providing shock absorption, and adding to stability of the joint.
The muscles acting on the knee can provide a variety of movements allowing flexion and extension, side to side movement, back to front movement (translation), and rotatory movements. The excursions of these movements are limited within normal ranges by ligaments which are soft tissue attachments that attach bone to bone. The principal ligaments of the knee are the Anterior and Posterior Cruciate Ligaments which prevent excessive translation and rotation of the bones relative to one another, and the Medial and Lateral Collateral ligaments prevent excessive side to side movement.
Injuries to any of these components may cause pain, loss of movement, and/or a feeling of instability within the knee.
Ligament Injuries
The Anterior Cruciate Ligament (ACL) is the most commonly injured ligament in the knee that may require surgery. The injury is more common in females. The usual mechanism of injury is where a twisting force is applied to the knee with the foot firmly planted. This is usually a non contact injury although it can also occur through contact. The athlete will often report hearing a “pop” or a “snap”. The knee may swell significantly. Usually the athlete will not be able to play on. Other injuries may occur concomitantly such as meniscal tears, articular cartilage damage, or damage to the collateral ligaments.
The result of this in many circumstances is a feeling of instability within the knee. The athlete will report a sensation of ‘giving way’ or of not trusting the knee. This is especially noted on pivoting of the knee.
After obtaining a history of the injury and performing a physical examination of the knee, surgery may be recommended. Your doctor may order an MRI scan to confirm the diagnosis and to diagnose other injuries that may have occurred within the knee. The decision to operate is based on a number of factors including the athlete’s age, occupation, level of sporting activity, and associated injuries. You may have a rehabilitation programme prescribed prior to any surgery.
Surgery involves reconstruction of the ligament usually using autograft tissue. This is the patient’s own tissue. Commonly used tissues include hamstring tendons or patellar tendon autografts. Occasionally allograft donor tissue may be used, which comes from another individual. Your doctor will discuss graft choices with you prior to surgery. At the time of surgery concomitant injuries of the knee may also be addressed.
Following surgery you can expect to be on crutches for between two and four weeks. Physiotherapy begins immediately post operatively. A structured rehabilitation programme aims to return the athlete to sport between six and eight months following the procedure. Your doctor may recommend a brace upon return to pivoting sports depending on other knee ligament insufficiency.
Posterior Cruciate Ligament (PCL) injury is far less common than to the ACL. It can usually be managed non-operatively and carries a favourable prognosis for return to sport.
Injuries to the collateral ligaments (MCL & LCL) can occur singly or in conjunction with cruciate ligament tears. Less severe grades of collateral injury can be managed non-operatively, but in more severe injuries or combined injuries surgery may be recommended. Combined injuries to the cruciate and collateral ligaments may carry a less favourable outcome for return to sport. It is under these circumstances your doctor may recommend a brace.
Meniscal Injuries
The knee has two meniscal cartilages between the femur and the tibia, one on the inside aspect (medial) and one on the outside (lateral). These crescent shaped structures are essential components of the knee acting to distribute load, providing shock absorption, and adding to stability of the joint. These may be damaged in twisting injuries, or as part of a degenerative process. They may also occur in conjunction with other injuries eg ‘O’Donoghues terrible triad’- ACL and MCL tears combined with a torn medial meniscus.
Symptoms of a damaged meniscus include pain within the knee joint (usually along the joint line), a feeling of instability within the knee, or an inability to fully straighten the knee. Swelling may also feature although it is not usually as marked as is seen in ACL injuries.
Many meniscal injuries will settle down of their own accord. With persistent symptoms surgery may be indicated. This will either involve removal of the damaged meniscal tissue, or occasionally a meniscal repair will be undertaken. This choice will depend on the location of the tear, the tear pattern, the age of the patient, and whether other injuries are also being addressed. Your surgeon will try to preserve as much meniscus as possible as meniscal deficient knees run a high risk of developing osteoarthritis (OA) later.
Articular Cartilage damage
The articulating surfaces of the knee are covered with a specialized tissue called hyaline cartilage. It is smooth and slippery to the touch and in conjunction with the joint fluid allows easy and painless knee motion. Hyaline cartilage has no blood supply and when injured has little capacity to heal.
Hyaline cartilage can be damaged by direct blows to the knee, and by shearing injuries such as in ACL tears. It can also be damaged by a natural degenerative process and this is called osteoarthritis (OA). Once cartilage damage occurs the end result is often OA. Therefore early treatment of these injuries can help prevent this problem, possibly saving the patient from salvage procedures such as Total Knee Replacement at a later date.
Techniques such as microfracture, Osteochondral Allograft Transplant Systems (OATS), and Matrix Allograft Chondrocyte Implantation (MACI) can be used. OATS involves transposing normal cartilage from non-weightbearing areas of the knee to the diseased area. MACI is where a small amount of cartilage cells are harvested from the knee. They are sent abroad to be cultured (multiplied) under strict aseptic conditions. These cells are then returned into the knee, embedded in a gel matrix at approximately six weeks after harvest. This is under a licence granted to Beacon hospital and Genzyme (system developers) from the Irish Medical Board (IMB). Currently this is the only hospital in Ireland licensed to carry out this procedure.
KNEE
IMPORTANT NOTICE: Please note you will need a referral letter from your GP to use any of
the services of UPMC Beacon Centre for Orthopaedics, except for the Physiotherapy department.