Osteochondral injuries of the knee (osteochondritis dissecans)
Overview
Osteochondritis is a condition of the surface of the knee joint where the surface becomes uneven and can develop into a loose piece of bone or cartilage that can float away. This results in swelling pain and occasionally looking in the knee.
Osteochondritis, most commonly occurs in teenaged children but can occur at any age.
What are the causes of osteochondritis?
The causes are as yet not fully determined but are thought to include:
A direct injury where something hits the surface of the bone, for example a cricket or hockey ball.
A repetitive strain type stress fracture in the bone from high impact activities that are consistently done over a period of time. This can include running jumping.
Low bone mineralisation, such as occurs when vitamin D is low.
There is also thought to be a component where the blood supply to the surface is impaired from an unknown cause.
There may also be a genetic component.
What are the symptoms of osteochondritis?
The most common symptom is a persistent pain, which usually is worse when doing impact activities.
Swelling and the feeling of water in the knee may also occur.
The sensation of something catching or popping in the joint: this may imply that the osteochondritis has led to a loose piece of bone in the joint.
Reduction in the range of straightening or bend in the joint: all the sensation of giving away.
When should I see a doctor if I suspect osteochondritis?
If the pain in the knee is persistent beyond six weeks, or there is a history of direct injury to the knee, or the knee is consistently swollen with catching or giving way, a specialist opinion would be advisable, probably with a MRI scan to investigate this
What could happen if this is not picked up and treated on time?
If the osteochondral injury becomes loose, the loose body can damage the rest of the bony surfaces of the joint. The place where it comes from can also start degenerating and this can lead to early osteoarthritis
How do we diagnose osteochondritis?
Diagnosis always starts with taking the story of what has happened to the knee, together with examining the knee for swelling, range of movement and tenderness. Occasionally, there may be an associated ligament injury which can be also be assessed.
Is an MRI scan required to diagnose osteochondritis?
In most cases an MRI scan is the best way of diagnosing osteochondritis.
MRI scans are done using a magnet, which are not taught which is not to cause any harm to the knee. It gives an idea of all the bony surfaces in the knee as well as the ligaments, cartridges and synovial lining of the knee.
How is osteochondritis treated?
Treatment of osteochondritis depends on whether your specialist will feel that the damage can heal on its own with a period of rest and physiotherapy.
If there is a risk that the bone is not going to heal, and is likely to loosen further, surgery may be required.
There are many factors that affect whether there is a likelihood of healing:
Age: the younger the patient, the more likely that the damage is to heal with the rest.
How long symptoms have been present for: if symptoms have been present for more than six months the likelihood of healing is less.
The appearance of the knee on examination: if there is swelling or restricting a range of movement in the knee, this may imply that the defect is unstable and require surgery.
MRI scan appearances: the size of the damage, whether there is a fluid signal at the base of the injury, and whether the osteochondritis looks loose.
Sometimes repeat MRI scans over 3 to 6 months are the best way to assess whether the injury is healing or getting worse.
What surgery can help heal osteochondritis?
The aim of surgery, will be to pin the defect back into position with either absorbables screws or tax, or metal screws.
Sometimes, simple drilling of perforation into the bone can help stem cells into the area of the defect from the bone marrow and stimulate healing.
If the defect is loose and the loose fragment is not healthy or fitting back into position, the loose fragment may require removal.
The bed of the defect can then be treated with either perforation/microfracture, or a membrane to cover this.
What are the risks of surgery?
As with all operations the risks include: new infection, bleeding, nerve or vessel damage,. These are unlikely and less than 1%.
The main "risk" can be that the defect does not heal and further surgery is required to remove the fixation and graft the defect with donor bone. This risk can vary between 5% and 15% depending on the original state of the defect.