Articular Cartilage or Joint Surface Injury

Arthroscopic Picture - Joint Surface Damage to Medial Femoral Condyle

Arthroscopic picture showing significant area of joint surface damage to medial femoral condyle.

Traumatic or Acute Injury

An injury to the joint surface may occur with any trauma to the knee. When a fragment of cartilage breaks free this causes severe pain, swelling and catching in the knee. It is occasionally possible to re-attach these loose fragments and reconstruct the joint surface.
The most common situation is that the fragments need to be removed with key hole (Arthroscopic) surgery. The damaged area may simply require tidying up or chondroplasty to remove any loose edges. If the joint surface damage is more significant then surgery can be carried out to try and encourage new cartilage to form, in the form of a Microfracture Procedure.


Articular cartilage has very low potential for self-repair. Once damaged, it does not tend to heal. Several procedures are available to regenerate joint surface cartilage in the form of Microfracture, OATS, and Cartilage Transplantation (MACI) though restoration to

complete normality is usually not possible.



Ligament injury

Ligament Injury - Knee Surgery

Any of the four major ligaments that stabilise the knee can be injured.

These include the two cruciate ligaments (anterior / ACl and posterior / PCL), which lie within the centre of the knee and cross one another hence their name.

The collateral ligaments are found on the inner/medial side of the knee (medial collateral ligament - MCL) and outer/lateral aspect of the knee (lateral collateral ligament - LCL) joint.


Normal ACL

Normal ACL

Anterior cruciate ligament - ACL

The Anterior Cruciate ligament (ACL) lies within the centre of the knee and controls rotation of the knee. It also controls forward movement of the shin on the thigh bone. When this ligament is torn, the knee feels unstable with any twisting activity. An individual who has torn their ACL can usually carry out straight line activity, but any side to side movement or twisting is associated with instability and is therefore difficult or not possible. The anterior cruciate ligament is much more frequently injured that the posterior cruciate ligament.

The ACL tends to be injured during sport when the knee undergoes a sudden twisting motion. This is usually a non-contact injury and classically occurs when an individual is trying to change direction. In the UK, the two most common sporting activities associated with this injury are football and netball. When an ACL ruptures there is often an associated popping, together with pain and swelling of the knee. Typically the swelling develops very quickly – often within the hour of the injury. If the injury occurs during sport, the patient is invariably unable to carry on playing. Subseqently, as the swelling settles and the patient returns to normal activity, the knee can give way especially when changing direction with walking and running.

Approximately 20% of patients are able to carry out normal activities in the presence of a torn ACL. The remaining 80% , have problems with any twisting activity and sport becomes difficult and often not possible. In the presence of a severe ACL injury, manual work may also become difficult. Most patients with this injury complain of “not being able to trust the knee”. This feeling of instability is associated with the knee giving way as well as recurrent pain and swelling. Every time the knee gives way, the important soft tissue structures within the knee can potentially be damaged. The most commonly injured structures are the joint surface cartilage (articular cartilage) and the meniscal shock absorbers. 60% of patients who have torn their ACL have an associated meniscal tear. If left untreated, this instability progressively leads to premature osteoarthritis. In children, the ligament tear can sometimes be repaired. In the adult knee, the ligament cannot be repaired and needs to be replaced/reconstructed in order for the knee to regain stability, and prevent further secondary damage in the future.


In the UK, average time from ACL injury to surgery is currently 18 months, whereas in other countries such as Australia, it is around 6 weeks. Therefore, in this country, most patients have lots of secondary damage by the time they have their ACL reconstructed, and reparable meniscal tears become irreparable.

Normal ACL
MRI Scan - Normal ACL

MRI scan through the middle of the knee showing a normal anterior cruciate ligament  (ACL)

Ruptured ACL
MRI Scan - ACL Rupture

MRI through the middle of the knee showing a torn ACL

Medial collateral ligament - MCL

MCL Tear
Torn Medial Collateral Ligament (MCL)

Intra-operative picture taken during key-hole surgery showing a torn medial collateral ligament (MCL)

MCL Tear
MRI Scan - Torn MCL

MRI through the middle of the knee showing a torn MCL

The Medial Collateral Ligament is the most commonly injured ligament of the knee. This ligament provides stability to the inner (medial) aspect of the knee. It  can be injured in isolation or in combination with other knee ligaments. It is tight when the leg is straight and is usually injured when a knee is knocked sideways. The severity of the injury will guide the treatment. If the ligament is injured in isolation then it can usually be treated without surgery by a simple knee brace. The knee is held bent and prevented from going straight for 4-6 weeks. This is extremely effective but must be implemented soon after injury. Chronic and severe MCL tears may require surgery.

MRI Scan - Torn PCL

MRI scan through the middle of the knee showing a torn posterior cruciate ligament (PCL)

Posterior cruciate ligament - PCL

The Posterior Cruciate Ligament (PCL) lies behind the ACL in the centre of the knee. It connects the thigh bone to the shin bone and controls backward movement of the shin bone. It is usually injured by a direct blow to the shin which causes excessive backward movement of the shin on the thigh. A common mechanism is for the shin to strike the dashboard during a road traffic accident. Most isolated posterior cruciate ligament injuries can be managed with non-surgical treatment and appropriate rehabilitation. This may involve the use of a knee brace.

Lateral collateral ligament / postero-lateral corner injury - LCL/PLC

The LCL and the postero-lateral corner stabilise the outer aspect of the knee. They tend to be injured in combination with other knee ligaments and are very rarely injured in isolation. The posterolateral corner (PLC) is a collective name for a group of structures located in the outer back corner of the knee. Following significant injury it may be possible to repair the torn structures. In neglected or chronic cases ligament reconstruction +/- realignment osteotomy surgery is usually indicated.

X-ray - Multi Ligament Injury - All four ligament torn

X-ray of the knee joint demonstrating a knee dislocation with a side view of thigh bone and front view of shin bone. The shin bone has rotated 90 degrees on the thigh bone tearing all four ligaments within the knee. This occurred as a result of a motorcycle accident

Multi-ligament injuries

Multi-ligament knee injury occurs when 2 or more knee ligaments are ruptured at the same time. These injuries are invariably associated with joint surface (articular cartilage) and or meniscal cartilage damage. There is a significant risk of injury to the major blood vessels and nerves around the knee. This serious and complex injury may require staged treatment in the form of more than one surgical procedure to stabilise the knee.


Knee anatomy

The knee joint is surrounded by a thick bag (capsule) and filled with synovial fluid, which keeps it lubricated. It lies between the thigh bone (femur) and the shin bone (tibia).


X-ray of Normal Lateral Knee

Normal Lateral Knee X-Ray

The knee is often discussed as a single joint, but it is actually comprised of two joints. The part of the knee formed between the end of the femur and the top of the tibia is called the tibio-femoral joint. The patello-femoral joint lies between the end of the femur and the kneecap (patella).


The bones of the knee joint are covered by a layer of smooth joint surface cartilage. This white, shiny lining of the knee allows smooth gliding of the joint surfaces. This lining is so smooth that the surfaces move without friction, like two ice cubes gliding on one another. This joint surface cartilage is also referred to as articular cartilage. If the joint surface cartilage is damaged either through injury or repeated wear and tear, arthritis develops. This form of arthritis is called osteoarthritis.


The other type of cartilage that we find in the knee is the meniscal or shock-absorbing cartilage ( "footballers cartilage" ). There are two meniscal cartilages in the knee, one on the inner (medial) side of the knee and the other on the inner (lateral) side. They sit between the curved lower part of the femur (femoral condyle) and the flat upper part of the tibia (tibial plateau). Their function is to share the load from the thigh bone to the shin bone (when walking) and to provide stability to the knee. Whenever the shock absorbers are damaged, their shock absorbing function is compromised. This in turn exposes the underlying articular cartilage to wear and tear and damage.

Important knee structures - view from the front
Knee Anatomy - view from the front

Important knee structures - view from the back
Knee Anatomy - view from the back


The knee is stabilised by 4 key ligaments. Sitting in the centre of the knee are the 2 cruciate or crossing ligaments. The front ( anterior ) cruciate ligament is called the Anterior Cruciate Ligament or ACL. This stops excessive forward movement of the shin on the thigh and more importantly controls rotation. The back or posterior cruciate ligament ( PCL ) prevents excessive backward movement of the shin on the thigh. Sitting either side of the knee are the collateral ligaments. On the inner or medial side is the Medial Collateral Ligament or MCL. On the outer or lateral side of the knee is the Lateral Collateral ligament. Further stability to the knee is provided by the back 'corners' of the knee, namely the postero-lateral and postero-medial corners of the knee, which may also be damaged at the time of injury.


The key muscles for knee flexion (bending) are the hamstrings, which are found at the back of the thigh. Conversely the muscles that straighten or extend the knee are the quadriceps, which sit at the front of the thigh. The quadriceps attach to the upper part of the kneecap (patella) via the quadriceps tendon. The lower part of the patella attaches to the tibia via the patellar tendon. An injury to any part of the “extensor mechanism” will prevent a patient from being able to straighten their leg and make walking very difficult.


Knee Injuries

Knee injuries are common, especially when taking part in sporting activities.

If you have a knee injury, and it is followed by pain and swelling in your knee, then it is extremely likely that you have damaged one of the important internal structures within the knee.


Most commonly injured are:

  • the menisci or shock-absorber cartilages
  • the knee ligaments - especially the medial collateral ligament (MCL) & Anterior Cruciate Ligament (ACL)
  • the lining (articular) cartilage of the knee joint


With high energy injuries, it is also possible to damage the bones that make up the joint - the kneecap (patella), the shin bone (tibia) and the thigh bone (femur)


Symptoms of knee injury include:

  • Pain – this can be localised or general
  • Swelling
  • Clicking
  • Instability / knee giving way - patients don't trust their knee
  • Locking - this is an inability to fully straighten the knee
  • Catching
  • Stiffness
  • Inability to bear weight or walk


Bone Bruises from ACL Rupture

Bone Bruises in Tibia and Femur following ACL Rupture

Seeking early diagnosis and treatment may enable patients to improve their level of activity and also improve their long-term outcome. In order to identify the cause of the knee problem, it may be necessary to carry out a variety of different tests including : X-rays, MRI, CT and ultrasound scans. It may also be necessary to look inside the knee with a key-hole procedure (arthroscopy), in order to identify exactly what the source of the problem is. The image to the right shows a bone bruise (seen in white on the scan) on both the tibia and femur - this is a common appearance following an ACL rupture.

Treatment options following knee injury :


  • Anti-inflammatory tablets and simple painkillers
  • Rest, ice, compression and elevation (RICE)
  • Activity and life-style modification
  • Physiotherapy (including muscle strengthening exercises)
  • Podiatry (including gait analysis)
  • Bracing (to stabilise the knee and restrict movement)
  • Injections (steroid, local anaesthetic, PRP - platelet-rich plasma and whole blood injection)
  • Shock wave therapy (for tendon problems)
  • Surgery



Mr Wilson during a knee consultation

Mr Wilson during a knee consultation

Mr Wilson examining a patient's knee

Key-hole  knee surgery

Key-hole knee surgery

Surgical team during knee arthroscopy

Anaesthetist - Dr Nick J looking over the drapes

Anaesthetist - Dr Nick J looking over the drapes

Orthopaedic consultation

Orthopaedic consultation

Anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstruction

Knee injection with PRP

Knee injection with PRP

Mr Wilson in surgery

Mr Wilson in surgery

Arthroscopic knee surgery

Arthroscopic knee surgery

Mr Wilson examining a patient's knee

Mr Wilson examining a patient's knee