Boys middle finger a little crooked may be caused by physiological factors, such as normal fingers with a certain degree of deviation, but both sides symmetrical and stable. It may also be caused by trauma, degenerative joint changes, rheumatoid arthritis and other diseases. 1. Trauma: After the joints are traumatized by external force, ligament damage may be caused, resulting in joint instability and easy deformity, which leads to the middle finger becoming crooked. 2. Degenerative joint changes: degenerative arthritis can cause degenerative synovial hyperplasia, synovial thickening, synovial edema, etc., so that the patient’s middle finger ligament damage, causing joint instability, resulting in the middle finger deformity to become bad crooked. 3. Rheumatoid arthritis: this disease can lead to narrowing of the joint space, excessive strain, cold, etc., causing a certain degree of osteophytes and thus leading to the middle finger deformity. Physiological factors when the middle finger is a little crooked is in the normal degree of deviation, generally do not need treatment. Excluding the symptoms caused by physiological factors, it is recommended that the patient consult a doctor in a timely manner to clarify the cause of the disease and follow the doctor’s instructions for standardized treatment.