Skin temperature of the shoulder: circadian rhythms in normal and pathologic shoulders

Circadian rhythm of the shoulder skin temperature was studied in 21 shoulders of 20 patients with rotator cuff tears (average age, 58 years) and 4 shoulders of 4 patients with rotator cuff tendinitis (average age, 34 years). Fourteen of the 23 uninvolved shoulders with no abnormalities on magnetic resonance imaging were also studied as normal shoulders. With a portable thermometer with the probes attached to the anterior surface of both shoulders, the skin temperature was recorded every 5 minutes from 1:00 PM to 9:00 AM (20 hours). Both the normal and cuff tear shoulders showed a similar circadian rhythm with the temperature at night significantly lower than the temperature during the daytime (P < .0001). On the other hand, the tendinitis shoulders did not show this circadian rhythm; the temperature did not change significantly through the range of measurement. We conclude that the skin temperature shows a circadian rhythm in normal shoulders, and this rhythm may be affected by certain pathologic conditions of the shoulder.