Table 1.

Nircahl's Stages of Tendinopathy¹⁶

Stage	Diagnosis	Macroscopic Pathology	Histologic Findings	Clinical Signs
0	Healthy	No inflammation	Organized collagen, absent blood cells	Firm tendon, not painful, absent swelling, normal temperature
I	Acute tendinitis	Symptomatic tendon degeneration, Increased cellularity; vascular disruption; inflammation of paratenon	Degenerative changes w/ microtears, inflammatory cells in paratenon; focal collagen disorientation	Acute swelling, pain, local tenderness, warmth, dysfunction
II	Chronic tendinitis	Increased tendon degeneration and vascularity	Greater evidence of microtears, increased levels of collagen disorientation in tissue hypercellularity	Chronic pain w/ tenderness, increased dysfunction, person voluntarily unloads structure
III	Tendinosis	Intratendinous degeneration due to microtrauma, cellular/tissue aging; vascular compromise	Increased celluarity, neovascularization, focal necrosis, collagen disorganization and disorientation	Palpable tendon enlargement, swelling of tissues, increased dysfunction w/ or w/o pain, tendon sheath may be swollen
IV	Rupture	Tendon failure	Complete disruption of fibers	Weak and painful muscle testing, inability to move affected joint, + clinical tests for tendon disruption