Familial osteochondritis dissecans

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Familial osteochondritis dissecans is a condition that affects the joints and is associated with abnormal cartilage. Cartilage is a tough but flexible tissue that covers the ends of the bones at joints and is also part of the developing skeleton. A characteristic feature of familial osteochondritis dissecans is areas of bone damage (lesions) caused by detachment of cartilage and a piece of the underlying bone from the end of the bone at a joint. People with this condition develop multiple lesions that affect several joints, primarily the knees, elbows, hips, and ankles. The lesions cause stiffness, pain, and swelling in the joint. Often, the affected joint feels like it catches or locks during movement. Other characteristic features of familial osteochondritis dissecans include short stature and development of a joint disorder called osteoarthritis at an early age. Osteoarthritis is characterized by the breakdown of joint cartilage and the underlying bone. It causes pain and stiffness and restricts the movement of joints.

A similar condition called sporadic osteochondritis dissecans is associated with a single lesion in one joint, most often the knee. These cases may be caused by injury to or repetitive use of the joint (often sports-related). Some people with sporadic osteochondritis dissecans develop osteoarthritis in the affected joint, especially if the lesion occurs later in life after the bone has stopped growing. Short stature is not associated with this form of the condition.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutation of the ACAN gene can cause familial osteochondritis dissecans. The ACAN gene provides instructions for making the aggrecan protein, which is a component of cartilage. Aggrecan attaches to the other components of cartilage, organizing the network of molecules that gives cartilage its strength. In addition, aggrecan attracts water molecules and gives cartilage its gel-like structure. This feature enables the cartilage to resist compression, protecting bones and joints.

The ACAN gene mutation associated with familial osteochondritis dissecans results in an abnormal protein that is unable to attach to the other components of cartilage. As a result, the cartilage is disorganized and weak. It is unclear how the abnormal cartilage leads to the lesions and osteoarthritis characteristic of familial osteochondritis dissecans. Researchers suggest that a disorganized cartilage network in growing bones impairs their normal growth, leading to short stature.

Sporadic osteochondritis dissecans is not caused by genetic changes and is not inherited.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Familial osteochondritis dissecans is a rare condition, although the prevalence is unknown. Sporadic osteochondritis dissecans is more common; it is estimated to occur in the knee in 15 to 29 per 100,000 individuals.

Understanding terms used in the source

These definitions explain medical words used above. A definition is not evidence that another condition is present, and it does not predict how a symptom will develop. Ask the clinician which terms apply to the actual examination or test result.

Osteochondritis dissecans

A joint disorder caused by blood deprivation in the subchondral bone causing the subchondral bone to die in a process called avascular necrosis. The bone is then reabsorbed by the body, leaving the articular cartilage it supported prone to damage. The result is fragmentation (dissection) of both cartilage and bone, and the free movement of these osteochondral fragments within the joint space, causing pain and further damage.

Osteoarthritis

Degeneration (wear and tear) of articular cartilage, i.e., of the joint surface. Joint degeneration may be accompanied by osteophytes (bone overgrowth), narrowing of the joint space, regions of sclerosis at the joint surface, or joint deformity.

Short stature

A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).

Single lesion

Applies to an abnormality whose distribution and appearance are solitary and localized to a part of the skin, a tissue or an organ that differs from the surrounding healthy tissue.

Affected

This term applies to a family member who is diagnosed with the same condition as the individual who is the primary focus of investigation (the proband).

Which doctor should you see?

The suggested department for discussing Familial osteochondritis dissecans is Orthopaedics, with a orthopaedic specialist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• What explains the change in pain, movement or function?
• Which activities need adjustment while the diagnosis is being clarified?
• What are the roles of rehabilitation, observation and surgery in this situation?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Familial osteochondritis dissecans. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.