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Counts remain separate, and an empty cell does not mean a feature cannot occur.</p>"},"coverage":{"countRecords":0,"emptyColumnKeys":[],"hpoRelease":"2026-06-23","narrativeSourceChanges":[],"records":18,"sourceGroups":{"omim":0,"orphanet":18,"published":0}},"features":[{"hpoId":"HP:0001367","label":"Abnormal joint morphology","primary":false},{"hpoId":"HP:0011843","label":"Abnormal musculoskeletal physiology","primary":false},{"hpoId":"HP:0002992","label":"Abnormal tibia morphology","primary":false},{"hpoId":"HP:0002815","label":"Abnormality of the knee","primary":false},{"hpoId":"HP:0002829","label":"Arthralgia","primary":false},{"hpoId":"HP:0010885","label":"Avascular necrosis","primary":false},{"hpoId":"HP:6000917","label":"Bone marrow edema","primary":false},{"hpoId":"HP:0003184","label":"Decreased hip abduction","primary":false},{"hpoId":"HP:0001288","label":"Gait disturbance","primary":false},{"hpoId":"HP:0001382","label":"Joint hypermobility","primary":false},{"hpoId":"HP:0001387","label":"Joint stiffness","primary":false},{"hpoId":"HP:0001386","label":"Joint swelling","primary":false},{"hpoId":"HP:0001376","label":"Limitation of joint mobility","primary":false},{"hpoId":"HP:0001377","label":"Limited elbow extension","primary":false},{"hpoId":"HP:0006376","label":"Limited elbow flexion","primary":false},{"hpoId":"HP:0000938","label":"Osteopenia","primary":false},{"hpoId":"HP:0003088","label":"Premature osteoarthritis","primary":false},{"hpoId":"HP:0009050","label":"Quadriceps muscle atrophy","primary":false}],"ledeHtml":"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. 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atrophy","onset_id":null,"reference":"ORPHA:2764","source_release":"2026-06-23"},"sourceGroups":["orphanet"]}],"referenceLabels":{},"references":{"causeHtml":"<ul><li><a href=\"https://medlineplus.gov/genetics/condition/familial-osteochondritis-dissecans\">Familial osteochondritis dissecans</a></li></ul>","identityNote":"MONDO cross-references identify native condition entries. Ancestor membership does not transfer phenotype values between groups.","importantHtml":""},"sections":[{"bodyHtml":"<p>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.</p><p>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.</p><p>Sporadic osteochondritis dissecans is not caused by genetic changes and is not inherited.</p><p class=\"section-source\"><a href=\"https://medlineplus.gov/genetics/condition/familial-osteochondritis-dissecans/#causes\">MedlinePlus Genetics: Causes</a></p>","key":"forms","title":"What causes Familial osteochondritis dissecans?"},{"bodyHtml":"<p>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.</p><p class=\"section-source\">Source: <a href=\"https://medlineplus.gov/genetics/condition/familial-osteochondritis-dissecans\">MedlinePlus Genetics</a></p>","key":"overview","title":"Condition overview"}],"sharedSources":[],"slug":"familial-osteochondritis-dissecans","sourceDocuments":[{"name":"Familial osteochondritis dissecans","reviewed":"2012-10","sections":{"causes":{"fetchedAt":"2026-10-20T20:21:26.940086+00:00","label":"Causes","pageSha256":"c42c7f05348cce4b34fa33d6c2809a44ccde9095f8c2c90a7f13a150edf31e9f","sourceUrl":"https://medlineplus.gov/genetics/condition/familial-osteochondritis-dissecans/#causes","status":"available"}},"source_release":"2026-10-01","url":"https://medlineplus.gov/genetics/condition/familial-osteochondritis-dissecans"}],"sourceNote":"MedlinePlus descriptions and Causes; original HPO annotations.","takeawayHtml":"Cause explanations are from MedlinePlus Genetics. Feature values below retain their original sources and patient groups.","title":"Familial osteochondritis dissecans"},"schemaVersion":1}