The patella is the largest sesamoid bone in the body, embedded within the quadriceps tendon and articulating with the patellar surface of the femur. It increases the mechanical advantage of the quadriceps by acting as a lever, but its tracking within the trochlear groove is frequently disrupted by muscle imbalance.
| Articulations |
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|---|---|
| Landmarks |
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| Ossification | Endochondral ossification from a single centre appearing between ages 3 and 6, with occasional secondary centres producing bipartite or tripartite patella in 2 to 6 percent of people. |
The patella is the largest sesamoid bone in the body, embedded within the quadriceps tendon to increase the mechanical advantage of the quadriceps by approximately 50 percent at full extension. Patellar fractures from direct blows or eccentric quadriceps contraction require fixation when the extensor mechanism is disrupted. Bipartite patella from separate ossification centres occurs in 2 to 6 percent of people and can be confused with fracture.
With the person lying down and the thigh muscles relaxed, hold the kneecap between your thumb and fingers. Trace its broad upper border (base), its inner and outer edges and its pointed lower end (apex). Gently glide it side to side and up and down to check its mobility.
A direct fall onto the knee or violent quadriceps contraction fractures the patella; displaced fractures disrupt knee extension and need fixation.
The patella usually dislocates laterally during twisting, tearing the medial patellofemoral ligament; it is common in adolescents with patellar maltracking.
Anterior knee pain around the patella aggravated by stairs, squatting, and prolonged sitting, common in young athletes.
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