Normal Intertarsal Joint Space Size on Radiography
The intertarsal joint spaces represent the articulations between the tarsal bones of the midfoot and hindfoot, including the subtalar, calcaneocuboid, and talonavicular joints. Accurate measurement on radiographs is essential for identifying early joint space narrowing, widening from ligamentous disruption, or bony coalition. Recognizing normal values helps clinicians differentiate physiological variation from pathological change in foot and ankle disorders.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Anteroposterior, Lateral | 2.0-2.5 mm |
Clinical Significance
On standard anteroposterior and lateral radiographic projections, a normal intertarsal joint space measures 2.0–2.5 mm. Uniform joint space within this range reflects intact articular cartilage and normal osseous alignment. Asymmetric narrowing below this threshold raises concern for degenerative or inflammatory arthropathy, while focal widening may indicate ligamentous disruption or a Lisfranc-type injury pattern involving the midtarsal column.
Joint space narrowing is a hallmark of osteoarthritis following trauma, particularly after calcaneal or talar fractures. Inflammatory arthritides such as rheumatoid arthritis and seronegative spondyloarthropathies can produce symmetric erosive changes with progressive space loss. Conversely, apparent widening or absence of a visible joint space may indicate tarsal coalition, either fibrous, cartilaginous, or osseous, which is an important diagnosis in younger patients presenting with rigid flatfoot and recurrent ankle sprains.
- Post-traumatic osteoarthritis (subtalar, talonavicular, calcaneocuboid)
- Rheumatoid arthritis or seronegative spondyloarthropathy
- Tarsal coalition (fibrous, cartilaginous, osseous)
- Lisfranc or midtarsal ligamentous injury with widening
- Septic arthritis or crystal deposition disease (gout, CPPD)
Reference: Moeller T. Normal Findings in Radiography. TFL. (2000).
Imaging Notes
Intertarsal joint spaces are assessed on weight-bearing anteroposterior and lateral radiographs of the foot whenever possible, as non-weight-bearing views may mask subtle widening or narrowing related to ligamentous laxity. On the AP projection, the talonavicular and calcaneocuboid joints are best profiled; the lateral view allows evaluation of the subtalar joint and the overall midfoot alignment. Joint space should be measured at its narrowest visible point, ensuring the X-ray beam is perpendicular to the joint of interest to minimize projectional distortion.
Oblique views (typically 30–45° medial oblique) may supplement standard projections to isolate individual intertarsal articulations. Comparison with the contralateral foot is recommended when unilateral pathology is suspected. If radiographs are equivocal, CT provides superior bony detail for coalition or fracture assessment, while MRI is preferred for cartilage and ligamentous evaluation.