Knee injuries – cruciate ligament

The knee is a complicated joint made up of three separate functioning joints

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What kinds of knee injury are there?

The knee is a complicated joint made up of three separate functioning joints with multiple ligaments and two types of cartilage.

There are four main ligaments within the knee, the medial and lateral collateral ligaments that run down the inside and outside of the knee and the two cruciate ligaments which are the two cross ligaments which sit within the middle of the knee joint.

Then there is articular (joint) cartilage, which covers the interior of the joint and is typically four or five millimetres thick.

The menisci are shock absorbing cartilages that sit between the weight bearing surfaces.

If there is injury to the knee, it is possible that more than one of these structures may be injured at the same time.

What are the cruciate ligaments?

There are two cruciate ligaments in the knee: the anterior (in the front) and the posterior (at the back).

The cruciate ligaments secure the stability in the knee in cooperation with other ligaments, the menisci and the muscles.

We now know that the morphology of these ligaments is more complex than we originally thought. Each ligament has individual bundles with different functions and roles.

How do injuries to the cruciate ligaments occur?

Injuries to the anterior cruciate ligament are more common than injuries to the posterior cruciate ligament.

The posterior cruciate ligament is most commonly damaged in connection with road accidents. When the posterior cruciate ligament is torn across, the shin bone will move backwards on the thigh bone.

A lesion of the anterior cruciate ligament happens mostly in sporting situations where the foot is planted. For example:

  • if the leg is locked and the body is pushed forward.
  • if the bent knee is forced in the opposite direction to its natural motion.
  • a twist, for example while skiing or playing sport.

    If the anterior cruciate ligament is totally torn across, the knee may become unstable and the shin bone will move forwards on the thigh bone.

    What are the symptoms of an anterior cruciate ligament lesion?

    • Often a click is felt - followed by pain. The person will normally fall to the ground and have difficulty weight bearing.
    • The knee swells rapidly within minutes due to blood accumulating in the joint from the bleeding anterior cruciate ligament.
    • There will be pain in the knee in the following days or weeks. However, this will slowly subside as will the swelling over the ensuing days or weeks.
    • When the knee is at rest, the cruciate ligament injury itself will not cause pain. However, it will feel unstable when any weight is placed on it and the patient will feel that they are not able to control their knee. This can cause further injuries in the knee, such as secondary cartilage damage or other ligament injuries.

      What can be done after an injury has occurred ?

      The RICE (rest, ice, compression and elevation) protocol must be followed immediately after an injury has occurred.

      Urgent assessment by a specialist must then occur. Patients are normally taken to a local casualty department to exclude a fracture/bone injury and then are normally referred on to an orthopaedic surgeon with a special interest in the treatment of such injuries.

      Rest

      The injured knee must be rested for the first 24 to 48 hours to prevent any further injury.

      Ice

      The damaged area must be cooled by using an ice-pack or a packet of frozen peas. The ice must never have direct contact with the skin or the patient could get frostbite.

      A cloth should be placed between the ice and the skin. Ice can be laid on the affected area for up to 20 minutes every hour, but for no longer than three hours in all.

      Ice treatment has been known to be effective for up to 24 hours after an injury occurred.

      Compression

      An elasticated support bandage is designed for this purpose. The compression must be firm but not so tight that it affects the blood circulation.

      Elevation

      The leg must be elevated above heart level if possible. It is most comfortable to lie down and elevate the limb with a few pillows. If you are sitting down, the legs can be raised on a chair or a table.

      This elevation should be maintained as much as possible for a few days.

      The knee should be examined by a doctor.

      How does the doctor make a diagnosis?

      The doctor will look for all possible injuries to the knee. However, in the acute phase, the knee may be so swollen that it is impossible to examine properly. The doctor may decide to put a splint on the leg and examine the leg again after 10 days.

      • The doctor will take a careful history obtaining from the patient exactly how the knee was injured, ie the mechanism of the injury; he will then carefully assess the knee for swelling, tenderness, range of movement and assess the individual ligaments for signs of instability.
        • To diagnose a cruciate ligament lesion, the doctor will look for instability of the knee joint. The doctor will examine whether it is possible to drag the shin bone slightly forward in relation to the thigh bone. This will be examined with the leg in various positions.

          An MRI is almost invariably ordered as this is an accurate soft tissue scan that allows the treating doctor to visualise the knee.

          • Major cartilage injuries that are blocking knee movements may need to be treated early by way of an arthroscopy and either resection or repair.
          • In the absence of these, management is usually initially non-operative with use of braces when necessary, ice, anti-inflammatories and physiotherapy to reduce swelling and restore range of movement.
          • The patient and the injured knee are carefully monitored over the ensuing weeks to assess recovery.

            Is surgery always necessary?

            No. This will depend on the patient's level of activity, job, age and especially how much trouble the knee causes.

            Frequently an isolated anterior cruciate ligament injury in someone of low activity can cause so few problems that physiotherapy and strengthening programme will be enough to avoid the need for reconstructive surgery.

            But even if surgery is not required, the patient should undergo a three-month programme of rehabilitation to strengthen the muscles that stabilise the knee. It is also important to continue to exercise in the future.

            How is surgery carried out for a cruciate ligament injury?

            Surgery is usually carried out under a general anaesthetic. The doctor will perform an arthroscopy of the knee and will look for any other damage that can be repaired at the same time.

            When the anterior cruciate ligament tears it usually tears its own blood supply and dies and therefore has to be replaced with another structure.

            The anterior cruciate ligament therefore is normally replaced or reconstructed with a donor ligament either from the patient's own body, usually part of the patellar tendon or hamstring tendons or a donor graft or Allograft from other people.

            The torn ligament is reconstructed using arthroscopic surgery most commonly using patellar tendon or hamstring tendons with these new ligaments being placed in the correct alignment within the knee joint to give the new anterior cruciate ligament as near as possible the original positioning and tensioning of the injured anterior cruciate ligament.

            What kind of recovery can be expected after surgery for a cruciate ligament injury?

            The patient will be able to walk again the day after surgery and may be given crutches or a hinged knee brace to wear.

            Patients are treated post operatively with physiotherapy and regular consultations with their treating surgeon.

            It is important that the knee and muscles are as functional as possible after a surgical operation and it will be necessary to undergo a rehabilitation programme lasting at least three months. However, during the first week after surgery, exercise should be limited or it will make the knee swell up.

            There are a range of post-operative regimes. Physiotherapy normally continues for anything up to three to six months, after a few weeks most patients are returning to light non impact exercise such as static cycling and cross training.

            Jogging and running can normally start at twelve weeks; a return to all sports is normally possible at six months.

            Knee ligament reconstruction is evolving all the time and results are steadily improving allowing more and more patients to return to their accident level of activity.

            Other people also read:

            Knee injuries – the articular cartilage: Find out what treatment is available?

            Arthroscopy: What happens during an arthroscopy?

            Anaesthesia: What does the anaesthetist do?

            Based on a text by Dr Hans Gad Johansen, specialist, Ejnar Kuur, consultant

            Last updated

            Consultant orthopaedic surgeon
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