Flat Iron vs Tendon — What's the Difference?
Quick Answer
Side-by-side
| flat iron | tendon | |
|---|---|---|
| Primal | chuck | offal |
| Muscle / location | Infraspinatus muscle, top blade of the shoulder clod | Connective tissue at joints — particularly the hock/lower leg |
| Character | The second most tender muscle on the entire animal, after the tenderloin. A flat, rectangular steak extracted from the top blade by splitting it along the central connective tissue. Uniform thickness makes it ideal for grilling. Also known as butler's steak in the UK. | Collagen-rich connective tissue extracted from the leg joints, particularly the Achilles tendon area. Extremely gelatinous when slow-cooked; provides body and sticky texture to braises and soups. Prized in Korean, Vietnamese, and South Asian cuisine for its chew and the richness it adds to broth. |
Key differences
- Different primals: chuck vs offal.
- Texture and slicing: compare fibrous, grain-heavy cuts vs more tender steak-style muscles based on each cut’s description.
- Retail naming diverges by country—always map through a canonical cut when translating menus or labels.
When to use each
Flat Iron
Pick Flat Iron when you want its specific marbling/texture profile: The second most tender muscle on the entire animal, after the tenderloin. A flat, rectangular steak extracted from the top blade by splitting it along the central connective tissue. Uniform thickness makes it ideal for grilling. Also known as butler's steak in the UK.
Tendon
Pick Tendon when its primal/muscle traits fit the dish: Collagen-rich connective tissue extracted from the leg joints, particularly the Achilles tendon area. Extremely gelatinous when slow-cooked; provides body and sticky texture to braises and soups. Prized in Korean, Vietnamese, and South Asian cuisine for its chew and the richness it adds to broth.
Flat Iron and Tendon are different canonical muscles/primals: Flat Iron is chuck (Infraspinatus muscle, top blade of the shoulder clod); Tendon is offal (Connective tissue at joints — particularly the hock/lower leg).
Choose based on tenderness, marbling, grain direction, and how you plan to cook (sear vs braise vs slice thin).
Read the full guides: flat iron (what-is) · tendon (what-is) · flat iron hub · tendon hub