Osteochondritis Dissecans In Knee

The knees are one of the most complex joints in our body. We need them to move in many directions and carry our weight.  The causes of knee pain vary widely and can be different between adults and children.  Osteochondritis dissecans (OCD - not to be confused with Obsessive Compulsive Disorder) is more often related to knee pain in children. Continue reading if you are interested in learning more about this condition.   

Introduction

Definition of osteochondritis dissecans 

Osteochondritis dissecans (OCD) is a condition where small pieces of bone and cartilage (the smooth tissue protecting the ends of bones) become detached. This occurs most commonly from the thigh bone (femur), and the fragments separate into the knee joint.¹ OCD can occur in any joints in the body, however the knee, ankle, and elbow are the most common sites where it is found.²

Significance in knee joint health

Joints are junctions between two bones that assist us in moving. The easy, uninterrupted movement we experience is due to the presence of cartilage, which ensures that the ends of bones move smoothly without rubbing against each other. OCD disrupts the normal function of a joint by introducing loose pieces of bone, which reduce the cartilage at the ends of the bone and impair joint movement. The knee joint primarily enables bending and straightening of the legs. However, if OCD affects the joint, these essential movements may become painful or restricted.  

Brief overview of pathophysiology

OCD is believed to be caused by a change to a bone’s blood supply during growth.¹ This causes fragments of the affected bone and overlying cartilage to stop growing, come loose, or even detach from the main bone.² The cause is currently not understood, however a few potential causes are theorized, including;³

• Repeated small traumas to the area damaging blood supply 
• Osteonecrosis - the piece of bone dying which has many causes
• Fat traveling in the bloodstream and blocking the blood supply to the bone (known as an embolus)
• A genetic condition known as familial dysplasia, where cases of OCD can be seen in many family generations⁴

Repeated trauma to the joint is deemed to be the most common cause.^2,3

Risk factors

Although OCD is not fully understood, several risk factors appear to underlie its development, including;^3,5

• Children and teenagers who train and compete in sports and athletics. OCD of the knee was historically described as ‘catcher’s knee’ owing to the number of cases in team sports
• Severe knee trauma
• Family history of OCD, or  have familial dysplasia 
• Male sex
• The position of the femur (thigh) and tibia (shin) at the knee joint may also put a person at higher risk of OCD

Clinical presentation

Symptoms

OCD symptoms can include;^1,2,6

• Knee pain, often unable to pinpoint exactly where it hurts
• Worsening pain when exercising
• Limping
• Joint swelling
• Children may be reluctant to be active
• ‘Catching’ or locking of the joint 

The symptoms can be caused by other knee problems, and so should be discussed with a medical professional. It is also possible to have OCD but not express any of these symptoms (or in other words, be asymptomatic), and the condition may be found during medical examination for another issue.¹

Physical examination findings

Clinical examination may show visible knee swelling, pain when touched, and stiffness when the joint is moved.⁶ Wilson’s test may also be carried out by a doctor. You may experience pain when turning the shin inward with the knee slightly bent, but it is relieved by the shin turning outwards.⁶  

Diagnostic imaging techniques

Medical imaging is useful in spotting OCD in the knee and assessing its severity. X-ray, magnetic resonance imaging (MRI), and computed tomography (CT) scans can all be used to identify cases of OCD.^1,2 An X-ray may be used to assess the extent of the damage, whilst MRI is useful to see damaged cartilage.² A CT scan will provide similar images to an X-ray but can look at extensive injury in very small slices to help assess what treatment is needed.³

OCD classification 

OCD can range from knees with very little damage and little or no symptoms, to considerably altered function depending on how far the condition has progressed.  OCD classification helps medical professionals to assess the severity of the condition along with what treatment may be most suitable. 

Many classifications assess OCD severity, but they broadly all fall into the following categories;^6,7

• Stage 1: the bone is damaged but remains securely covered by cartilage
• Stage 2: the bone fragment is still in place but there is less bone supporting it
• Stage 3: the bone fragment is fully detached, although it remains in place and may shift
• Stage 4: the bone fragment is no longer in place and moves freely within the joint

Management approaches

There are many different opinions on how best to treat OCD,¹ but damage classification, the patient’s symptoms, and age will guide the best course of management.²

Non-surgical management

Rest and activity modification

OCD symptoms can sometimes resolve without need for medical intervention. Rest is often recommended, including reducing or completely avoiding the aggravating activity to allow for improvement.^2,3 Joint restriction or immobilization with a splint to allow cartilage recovery is also recommended.⁸   

Physical therapy

Physiotherapy such as stretching, muscle strengthening, and muscle activation exercises may be recommended to aid in recovery.⁸ The use of electrical stimulation therapy, hydrotherapy, and cryotherapy are also used.⁸

Surgical management

Indications for surgery

Surgery may be considered in patients where;^2,6

• Non-surgical techniques have failed to improve symptoms
• The bone fragment is detached and freely moving (Stage 4)
• A large bone fragment is affected in an older child, as their reduced growth and repair capacity make natural healing less likely
• Worsening damage is seen on medical imaging

Surgical techniques

There are many surgical options for OCD, and their strengths and complications should be discussed with a medical professional. Surgical options include;^2,6,8

• Drilling into the damaged bone to encourage healing through new blood vessel formation
• Using surgical pins and screws to hold the detached bone fragment in place
• Removal of the bone fragment
• Bone fragment replacement by bone and/or cartilage graftsKnee replacement in older adult patients

Post-surgery, weight-bearing through the affected knee will not be possible. Therefore, healthcare professionals will find the best way for you to mobilize, possibly with crutches.² Weight-bearing through the knee will commence at around six to eight weeks post-operation8.

Prognosis and complications

Many cases of OCD in the knee improve and resolve completely on their own with rest.² However, this can be a lengthy recovery, taking up to a year.³ Generally, younger patients have the best recovery from OCD as their joints are still growing and maturing, so they heal as they grow.⁶ Joint healing may also depend on where the bone fragment has become detached.⁶ OCD requiring surgery is at higher risk of complications, including an increased risk of osteoarthritis in the affected joint.³ Surgery also does not always resolve all symptoms, and so patients may still experience pain and issues with moving their knee even after an operation.³ 

Prevention strategies

As the causes of OCD are still not completely understood, it is difficult to make concrete recommendations on how to prevent the condition from developing.⁵ Many risk factors are beyond a patient’s control, and others, such as physical activity, can be modified to prevent injury, although they are also an important part of a healthy lifestyle.⁵ 

Therefore it is important to take any symptoms suggestive of OCD of the knee seriously and seek medical advice if they appear so that physical examinations can be carried out. Worsening damage to the bone can intensify the symptoms, classification, and prognosis, so it is important to seek prompt medical advice if OCD is suspected. 

Summary

Osteochondritis dissecans (OCD) is a condition that can affect any joint in the body but is mainly associated with the knees, ankles, and elbows. The way OCD develops is not fully understood, however, it causes damage to the cartilage and ends of bones. This is possibly due to damage to the blood vessels providing the growing bone and cartilage with nutrients. Traumatic injury to the joint, osteonecrosis, and hereditary dysplasia may also contribute to its development. OCD is often seen in physically active children and adolescents. Sometimes there are no symptoms, and it is incidentally found during other investigations, but OCD can cause knee pain, joint swelling, and stiffness or limping.

Medical imaging is key in diagnosing OCD.  X-rays and MRIs in particular are used to assess and classify the condition to guide treatment. Non-surgical approaches to treatment include rest and reduction of aggravating activities. Surgery may be considered in more severe cases, or where other treatments have failed. However, surgery does carry a risk of not improving symptoms or developing osteoarthritis.

A few factors govern the prognosis for OCD, but generally, younger patients have the best recovery, owing to their bones still growing, with increased potential for repair. As OCD is not fully understood, it is difficult to create a plan to prevent its development. Any symptoms suggestive of OCD should be discussed with a medical professional promptly to ensure optimal management.