We evaluated the natural history of partial rotator cuff tear using MRI. We examined 45 cases with partial rotator cuff tear (average age 71.0 years old) from May 2003 to October 2008 and who were performed on MRI and who underwent conservative treatment and were performed on MRI regularly. We classified the shapes of tears end into 4 groups(abnormal signal type, abnormal signal and swelling type, cut off end type, tapered end type) and evaluated atrophy and fat degeneration of rotator cuff muscle belly, using MRI, age, cause of pain, and the symptom change. The number of each type was abnormal signal type; 25 cases, abnormal signal and swelling type; 7 cases, cut off end type; 10 cases, tapered end type; 5 cases. The abnormal signal type almost showed a little change of the shape, and long term symptom. The 1/2 of the cut off end type changed into tapered end type. The tapered end type showed no change of the shape, and led to a little symptom. Regarding the shape of the torn end, 35 cases out of 47 cases(74.4%) showed no change, 12 cases(25.6%) got worse, 0 cases(0%) improved. Regarding to the shape and signal of the torn end, 25 cases out of 47 cases(53.2%) showed no change, 19 cases(40.4%) got worse, 3 cases(6.3%) improved. Atrophy of the muscle belly and fatty degeneration showed no significantly time-dependent change among the 4 types. We concluded that the tapered end type showed no change and the symptom was almost disappeared.
