The goal of this study is to verify the effect of vitamin D3 combined with extensor muscle strengthening exercise in lateral epicondylitis of elbow Are there significant differences in the improvement of functional scores between the study and control groups? Are there significant differences in the improvement of sonographic findings and blood D3 levels between the study and control groups? Participant will underwent D3 injection or saline injection and extensor muscle strengthening exercise with counter force brace. All the participant will undergo functional scoring, sonographic examination and blood D3 level testings until 6 months after initial visit.

Inclusion Criteria:

• lateral epicondylitis(LE) of elbow symptoms that persisted of increased for more than 3 months in which LE was defined as pain on the lateral side of the elbow and pain at the lateral epicondyle upon direct palpation and during resisted dorsiflexion of the wrist

Exclusion Criteria:

• younger than 20 years
• history of ipsilateral elbow surgery
• common extensor tendon tears more than 30% in depth
• inflammatory diseases (rheumatoid arthritis, psoriatic arthritis, etc)
• osteoarthritis with a limitation of range of motion (flexion contracture >30 degree and further flexion < 100 degree)
• neurological deficits in the ipsilateral upper limb,and follow-ups less than 24 weeks

Our IRB does not permit

An independent nurse uses a random sequence generator and allocates the participants into the two groups. Participant, investigator and outcomes assessor were blinded of participants' information