Though a lamb obviously has legs at the front and back, “leg” generally means rear legs, with “Foreshank” being used to refer to the front legs.
A rear lamb leg has two main cuts in it. The top half is the sirloin section; the bottom half is the shank section.
The top (aka sirloin) part of the leg has the most meat, and a hip bone in it. It is sometimes referred to as the “fillet”, but given that “fillets” are cut from all over the lamb, this isn’t as helpful a term as those using it might think.
The shank portion has a round bone in it.
Alternatively, the leg can be cut as a “Short Leg” or “3/4 leg.” This cut includes the bottom half of the leg (the shank), plus half of the top (the sirloin.) (That makes 2/4 plus 1/4, if you’re doing the math in your head.) The butcher could use the remaining 1/4 of the leg, which is the remainder of the sirloin, for lamb sirloin chops (aka lamb steaks.)
You can also get a “Centre Cut Lamb Leg”, which is half a lamb leg, except it contains half of the sirloin, and half of the shank.
Sometimes, instead of “top” and “bottom” of the leg, you may see, confusingly, the “top” of the leg (sirloin) referred to as the “foremost” section, and the “bottom” (shank) section referred to as the “hindmost” section.
The entire bone in the leg can be removed by a butcher. When boned, it can be rolled and stuffed and tied, or left flat to be used as a butterflied leg. Or, the leg can have the bottom bit of the shank bone hacked off (American style), or exposed (Frenched.)
The entire leg is covered in fell.
Lamb leg is expensive.
A whole leg is usually roasted.
Carving Tip: Cut slices parallel with the bone. Carve the sirloin end separately from the shank end. The shank end is narrower than the top sirloin end, so the meat in the shank end will be cooked more than the top — serve these shank end slices to the “well-done” crowd.
Because lambs raise themselves off the ground using their right leg to push up, the Ottoman nobility preferred left lamb legs, thinking them more tender.