Normal Tarsometatarsal Joint Space Size on Radiography
The tarsometatarsal (TMT) joints, collectively known as the Lisfranc joint complex, form the articulation between the distal row of tarsal bones and the bases of the five metatarsals. Accurate measurement of the TMT joint space on weight-bearing radiographs is essential for detecting subtle ligamentous disruption, fracture-dislocations, and degenerative joint disease.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Anteroposterior, Lateral | 2.0-2.5 mm |
Clinical Significance
A normal TMT joint space of 2.0–2.5 mm should appear symmetric and uniform across all five articulations on both anteroposterior and lateral views. Asymmetric widening—particularly at the first and second TMT interval—is a hallmark of Lisfranc ligament injury, which can be missed on non-weight-bearing studies. A gap exceeding 2–3 mm between the base of the first and second metatarsals compared with the contralateral foot is considered abnormal.
Narrowing of the joint space below 2.0 mm suggests degenerative or post-traumatic osteoarthritis, which frequently follows unrecognized or inadequately treated Lisfranc injuries. Uniform joint space narrowing across multiple TMT articulations may reflect inflammatory arthropathy such as rheumatoid arthritis or gout.
- Lisfranc ligament injury — widening, especially at the 1st–2nd TMT interval
- Post-traumatic osteoarthritis — joint space narrowing after prior injury
- Rheumatoid arthritis — symmetric narrowing with periarticular erosions
- Gout — asymmetric narrowing with overhanging edge erosions
- Charcot neuroarthropathy — fragmentation, dislocation, and collapse of the TMT complex
Reference: Moeller T. Normal Findings in Radiography. TFL. (2000) ISBN:3131646713.
Imaging Notes
TMT joint space measurement is performed on standard anteroposterior and lateral foot radiographs. Weight-bearing (stress) views are strongly preferred, as non-weight-bearing projections may fail to reveal dynamic instability and subtle widening. On the AP projection, the medial border of the second metatarsal base should align precisely with the medial border of the intermediate cuneiform; any offset warrants further evaluation. An oblique view at 30° internal rotation supplements assessment of the lateral TMT joints.
Measure the joint space at its narrowest visible point perpendicularly across the articular surfaces. Bilateral comparative views improve diagnostic sensitivity when asymmetry is suspected. Beam centering and patient positioning must be standardized, as oblique angulation artificially widens or narrows the apparent joint space and can mimic pathology.