Chondral defects

Articular Cartilage (chondral) localised Defects/Damage.

Introduction.

The moving surface of the knee is lined by articular cartilage.  The structure and functions of articular cartilage is outlined here.

Generalised damage to the articular cartilage, as can appear with degenerative conditions, is usually generalised and generically can be termed osteoarthritis.

However isolated lesions of an non-degenerative nature, can also occur of which there are two types:

* Traumatic
* Developmental condition called osteochondritis dessicans (OCD)

Traumatic Osteochondral Damage to the Articular Surface of the Knee.

As implied by the name, these lesions occur associated with traumatic injuries to the knee.  They can occur in any part of the knee joint, but most commonly are found on either the femoral condyles or in the patello-femoral articulation.

They can happen as a result of direction compaction injuries, such as can occur to the patello-femoral joint, if for example, the knee is struck against a car dashboard in a road traffic accident. Compaction injuries occur when two areas of the joint hit each other causing bleeding in the bone, as can be seen in the MRI scan below.

The more common mechanism for traumatic osteochondral defects is usually a rotational injury to the knee.  The mechanism to cause an osteochondral lesion is usually a shearing force across the articular cartilage. For adequate shearing forces to occur, tearing of a major ligament must occur to the knee, the most common of which is anterior cruciate ligament tear.  The other common site of significant shearing forces developing, is at the patello-femoral joint, when a patella (knee cap) dislocation occurs.

The severity of damage to the articular surface can vary across a spectrum, with one end being a crushing injury to the articular cartilage with no actual loss of continuity of the articular cartilage.  The other end of the spectrum is a piece of articular cartilage, with or without the underlying bone being physically knocked off from its original bed.  The type of lesion is dependent on the magnitude of the force of injury and the directional vectors of the resulting force, as well as any associated injuries to the knee.

Osteochondral/chondral injuries are commonly associated with major ligament injuries to the knee and also with meniscal injuries.

Clinical Presentation.

A detailed history taken from the injured person will normally indicate the mechanism of injury.  For example a direct compaction injury, associated with a road traffic accident, versus a rotational injury that can commonly occur, for example when changing direction in football.  Depending on the severity of the injury, the injured person may present with a localised pain and a mild swelling all the way through to a tense haemarthrosis (blood filling the joint) and possibly a locked knee.

Localised compaction injuries are treated symptomatically with ice, elevation, anti-inflammatories and routine physiotherapy modalities.  They can be diagnosed on MRI scanning, as below, although the scan below shows a compaction pattern that is typical for ACL tears.

This MRI scan shows the typical bone compaction pattern of an ACL tear. The compacted areas appear white due to the fluid (blood) in the "bruise".

If an actual piece of cartilage or bone and cartilage has been knocked off, the patient tends to get more bleeding and therefore a more tense haemarthrosis.  If the loose piece floats around within the knee, it can actually become physically stuck and cause the knee to lock so as to prevent certain movements until the piece moves out and 'unlocks'.

In the chronic situation, once all the acute symptoms have settled, the injured person will usually complain of intermittent locking and can also complain of instability symptoms, where the loose piece can get trapped in the knee and make the knee feel like it is going to give way, or may occasionally even truly give way.

The examination of the knee depends on whether the injured person is seen acutely following the injury or chronically at some later time.  In the acute situation, the knee is usually swollen with a reduced range of motion and generalised pain.  There may be associated ligament instabilities which are clinically detectable.

In the chronic situation, there may be a mild effusion (fluid within the joint).  The injured person may complain of a feeling of a loose piece floating within the knee, which is sometimes actually physically palpable within the knee.  If the knee is locked at the time of examination, the injured person will have a reduced range of motion with a true mechanical block to further motion.  Once again associated ligament instabilities may be clinically detectable on examination.

Imaging/Radiology.

All patients will routinely have a 4-view series of x-rays of the knee.  This may reveal in the case of an osteochondral injury, an alteration in continuity of the outline of the bone.  (Show picture).  Alternatively the plain x-rays may be normal.  It is important to assess the patello-femoral joint, as these can be origin of the defect, which may not be visible on routine x-rays without a skyline view.  (Show picture).

The diagnostic investigation for articular cartilage injuries to the knee is MRI scanning.  MRI scans will commonly reveal a loose fragment (show picture), or may reveal the area of damage to the articular cartilage, with the overlying cartilage still being intact (show picture).  If there is a loose fragment, the origin of this will commonly be identified on the MRI scan (show picture) and any additional ligament or meniscal damage can also be identified.

The KneeDoc is fortunate to have access to a high-resolution 3 Teslar MRI scan which with appropriate sequences is ideal at showing articular cartilage damage much more clearly and with greater accuracy than a normal resolution scanner (show picture).  It is not uncommon for articular cartilage injuries to be missed on a routine scan, to then be picked up on a high resolution MRI scan.

Other investigations that occasionally are used include CT scanning and even Bone (SPECT) scanning.

Treatment

In the acute phase, the treatment consists of resting the joint, elevation, ice, compression, anti-inflammatories and routine physiotherapy modalities.  As the swelling and pain diminish, it is important to commence range of motion exercises to regain movement of the knee fully.

Occasionally in the situation of a tense haemarthrosis, the knee can be aspirated under sterile conditions to remove the blood from within the joint, and some local anaesthetic can be injected into the knee to help with pain relief.  The aspirated blood should be placed into a container and left to stand.  If the injury involves a fracture of the underlying bone, in other words if the damaged fragment that has been knocked off includes cartilage and bone, then usually droplets of fat from the bone marrow are released into the knee and these are visible in the aspirated fluid and will float to the top pf the aspirated blood if left to stand.

The subsequent management of this condition depends on whether the presentation is acute or chronic.

Acute

The treatment in this situation depends on the size and thickness of the fragment that has been knocked off and the age of the patient.

* In a child with open growth plates, if a full thickness piece of articular cartilage has been knocked off to expose the underlying bone and the fragment is of a large enough size, it may be worth operating on the knee to find the loose fragment and reattach it to its original bed and hope that the articular cartilage fragment will heal to the underlying subchondral bone.  This however, does not always occur and should it not heal down and continue to cause symptoms, then the piece will have to be removed.  In a child however, it is certainly worth attempting to reattach the fragment.

* In an adult with closed epiphyses, if the piece that has been knocked off is purely articular cartilage, then this piece should be simply removed and the donor bed of bone can be treated appropriately, as in the case of a chronic osteochondral fragment (link).  In the adult, the articular cartilage really has no capacity to heal to the subchondral bone and attempting to reattach it is usually a futile exercise which will cause the injured person ongoing pain and instability type symptoms and further locking should the piece fall off again.

* If the chondral piece is associated with a significant fragment of osteochondral bone, and the piece is large enough, over 2 cm in diameter, then it is certainly worth attempting to reattach the fragment and fix it in place in both the adult and child.   The bone fragment will certainly heal to the underlying bone, but whether the overlying cartilage will heal and attach to the surrounding cartilage, is not guaranteed, but it is worth trying due to the underlying bone attachment.  If the underlying cartilage fragment does not heal, then once again, this can be removed at a later stage and treated as for a chronic injury.

Chronic Injuries

The acute phase treatment outlined above can certainly be attempted within the first seven to ten days of an injury of the knee.  If there is a large attached bony piece to the articular cartilage fragment that has been knocked off, then given up to two weeks, it may be feasible to reattach it.  However, once beyond this point, there is really not much point attempting to reattach the fragment as it is unlikely to heal, and in this situation the chronic treatment options are used.

* If there is a loose piece within the knee of articular cartilage and/or bone, this is removed.  The exposed bone bed is then treated using a debridement (tidying up) of the edges of the articular cartilage fragment to trim any loose pieces or flaps of articular cartilage (link to video).  The bone bed can be microfractured or drilled (link).  The aim of this technique is to cause infill into the osteochondral defect, which usually will occur with fibrous (scar) tissue.

* Other options for the chronic situation include mosaicplasty (link), which involves taking a plug or plugs of articular cartilage and bone from elsewhere within the knee and transplanting these into the defect. 

* Another, more debated, and currently state of the art technique, would be to undertake autologous articular cartilage transplantation (link), the theory of which would be to cause normal hyaline articular cartilage to re-grow in the defect.

It is important to address any underlying ligament instabilities either at the same time, or shortly afterwards so as to stabilise the knee and to protect whatever technique of treatment that has been undertaken to the articular cartilage damaged area.  This may include anterior cruciate ligament reconstruction and patello-femoral stabilisation.

---

Bookmark this page