What is Subluxation?
Subluxation is a partial or incomplete displacement of a joint where the articular surfaces lose their normal anatomical relationship but remain in partial contact, distinguishing it from complete dislocation where contact is entirely lost.
Context-Specific Definitions
The term "subluxation" has distinct meanings depending on the anatomical location:
Dental Subluxation
A subluxated tooth presents with abnormal mobility but no displacement, with sulcular bleeding present at the margin of the tooth and gums. 1
- This distinguishes it from concussion (tender but no mobility or displacement, no sulcular bleeding) 1
- It differs from luxation injuries where actual displacement occurs (lateral, extrusive, or intrusive) 1
- The key diagnostic features are increased tooth mobility without positional change and presence of gingival bleeding 1
Hip Subluxation (Developmental Dysplasia)
In developmental dysplasia of the hip (DDH), subluxation represents mild malposition of the femoral head within the acetabulum, part of a spectrum ranging from joint laxity to fixed dislocation. 1
- DDH comprises abnormal acetabular shape (dysplasia) and malposition of the femoral head, with subluxation being an intermediate stage between dislocatable hip and complete dislocation 1
- Most subluxations identified in newborns (60-80% on physical exam, >90% on ultrasound) resolve spontaneously 1
- Untreated cases can lead to early degenerative joint disease and impaired function 1
Patellar Subluxation
Patellar subluxation involves incomplete lateral displacement of the patella from the trochlear groove with spontaneous reduction. 2
- Weight-bearing axial radiographs should be obtained to evaluate patellofemoral kinematics and demonstrate the degree of patellar tilt or subluxation 2
- This differs from complete patellar dislocation where the patella remains displaced until manually reduced 2
Clinical Significance
The critical distinction is that subluxation involves partial loss of joint congruity with maintained contact, whereas dislocation represents complete separation of articular surfaces. 1
- In post-surgical contexts (hip replacement), subluxation represents clinically recognized incomplete movement of the femoral head outside the acetabulum with spontaneous reduction 3
- Subluxation often causes patient concern about potential dislocation and may alter behavior patterns 3
- The term requires anatomical context for precise interpretation, as definitions vary by joint and clinical specialty 4