Thigh

The femur is the thick, heavy bone of the thigh. Projecting medially off its upper inner end, from a variably long or short neck, is the head. Humans have the longest neck, then the carnivores, and then the ungulates, where the head appears to attach directly to the top of the shaft. The head articulates with the socket in the side of the pelvis, forming the hip joint. The outer side of the top end of the femur expands into the greater trochanter, which, although for the most part covered with thin muscle, forms a prominence on the surface. In the horse, it is completely covered by muscle of a medium thickness, but its form is still evident. Horses, rhinos and tapirs have a third trochanter—a prominent bony knob located one-third of the way down the outside of the femur, to which the gluteus superficialis muscle inserts.

The lower end of the femur expands into the spool-like trochlea in front and the two large condyles in back. The trochlea is notched in front to receive the ridge on the back of the patella (kneecap). In the horse, when the knee is extended (straightened), the front edges of both sides of the trochlea may occasionally be seen on the surface behind the patellar ligament. Only the condyles, projecting backward, articulate with the tibia at the knee joint.

The patella, or kneecap, glides in the groove of the trochlea when the knee is flexed and extended. The anterior thigh muscles attach to the patella. The bottom of the patella is attached to the tibial tuberosity via the patellar ligament(s). Because the patellar ligament does not change length, the distance between the patella and the tibia never changes, regardless of the position of the knee joint. In the standing horse and ox, with the thigh relaxed, muscles (or fat) above the patella can overhang and conceal it. The patella is then found at the base of a depression.

LEFT REAR LIMB OUTSIDE VIEW FRONT

PATELLA MOVES BACK RELATIVE TO FRONT

EDGE OF LOWER LEG WHEN KNEE IS FLEXED; LENGTH OF PATELLAR LIGAMENT REMAINS THE SAME.

PATELLAR LIGAMENT

PATELLAR LIGAMENT

Animal Leg Anatomy

EXTENDED LEG

Animal Leg Anatomy
FLEXED LEG

(FROM SPECIMENS)

EXTENDED LEG

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