Hashimoto's thyroiditis is an autoimmune disease associated with antimicrosomal antibodies. Thyroid failure from any cause can lead to hypothyroidism which has numerous manifestations, including rheumatic. Rheumatic or musculoskeletal symptoms may be the initial presentation of hypothyroidism. A case is described in which knee pain was the presenting symptom in a patient with Hashimoto's thyroiditis without any other sign or symptom of hypothyroidism. Synovial fluid was non-inflammatory and lab tests were consistent with hypothyroidism secondary to Hashimoto's thyroiditis. The non-inflammatory arthralgia and arthritis, stiffness and musculoskeletal signs of hypothyroidism were completely reversible with adequate thyroid replacement hormone. Knee effusions are a common sign in hypothyroidism with a sluggish bulge sign, which is due to highly viscous synovial fluid. Purpose of this case is early diagnosis and treatment of hypothyroidism by primary care physicians, which can probably prevent many patients from developing polyarthritis associated with hypothyroidism.