Traits

Traits linked to COL9A2

collagen type IX alpha 2 chain

The Human Phenotype Ontology links 62 traits to COL9A2, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of limbs

Trait	How often it is seen
Limb undergrowth	Often (30–79%)
Reduced arm span	Often (30–79%)
Abnormal kneecap	Sometimes (5–29%)
Abnormal radial epiphysis morphology	Sometimes (5–29%)
Abnormality of end part of the elbow bone	Sometimes (5–29%)
Abnormality of the ankle	Sometimes (5–29%)
Abnormality of the end part of the foot bone	Sometimes (5–29%)
Abnormality of the knee	Sometimes (5–29%)
Bilateral coxa valga	Sometimes (5–29%)
Broad femoral neck	Sometimes (5–29%)
Coxa vara	Sometimes (5–29%)
Fragmentation of end part of the long bone of hand	Sometimes (5–29%)
Knock knees	Sometimes (5–29%)
Outward bow-leggedness	Sometimes (5–29%)
Radially deviated wrists	Sometimes (5–29%)
Tibial torsion	Sometimes (5–29%)
Ulnar deviated club hands	Sometimes (5–29%)
Flattened end part of knee bone	Not recorded
Knee osteoarthritis	Not recorded
Short palm	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Abnormal development of end part of bone	Always
Abnormal shape of end part of bone	Very often (80–99%)
Double-Jointed	Often (30–79%)
Hip joint pain	Often (30–79%)
Irregular vertebral endplates	Often (30–79%)
Knee pain	Often (30–79%)
Abnormal formation of the hip	Sometimes (5–29%)
Degenerative joint disease	Sometimes (5–29%)
Flattened vertebrae	Sometimes (5–29%)
Foot pain	Sometimes (5–29%)
Osteochondritis dissecans	Sometimes (5–29%)
Scoliosis	Sometimes (5–29%)
Spondyloepiphyseal dysplasia	Sometimes (5–29%)
Muscle tissue disease	Rarely (1–4%)
Muscle weakness	Rarely (1–4%)
Flat end part of bone	Not recorded
Irregular end part of long bone	Not recorded
Small end part of bone	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Midface retrusion	Always
Short chin	Always
Flat face	Very often (80–99%)
Little lower jaw	Often (30–79%)
Zygomatic flattening	Often (30–79%)
Decreased number of teeth	Sometimes (5–29%)
Frontal bossing	Sometimes (5–29%)
High palate	Sometimes (5–29%)
Cleft palate	Rarely (1–4%)

Abnormality of the eye

Trait	How often it is seen
Retinal detachment	Always
Severe near sightedness	Always
Vitreoretinopathy	Always
Abnormal vitreous humor morphology	Often (30–79%)
Close sighted	Often (30–79%)
Clouding of the lens of the eye	Often (30–79%)
Lattice retinal degeneration	Sometimes (5–29%)

Constitutional symptom

Trait	How often it is seen
Fatigue	Often (30–79%)
Joint pain	Often (30–79%)
Postexertional symptom exacerbation	Often (30–79%)

Abnormality of the nervous system

Trait	How often it is seen
Waddling gait	Sometimes (5–29%)
Wide based walk	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Short stature	Always
Mild short stature	Not recorded

Abnormality of the ear

Trait	How often it is seen
Sensorineural hearing impairment	Always

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to COL9A2 and how often each is seen. Find out more at hpo.jax.org.

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