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Figure 2: (a) Masson’s trichrome staining of postnatal day 1 patella with patellar and quadriceps tendon in mouse at 4x. (b) Higher magnification (100x) shows patellar tendon composed of parallel collagen fibers (blue) with cells aligned almost parallel to fibers. Enthesis in rectangle (i.e., quadriceps tendon insertion on patella) is shown (a). Higher magnification of enthesis at 20x (c) and at 100x ((d) and (e)). Collagen fibers (blue) show penetration on patella (d) and ending on patella ((e), yellow arrows).