Stiff pinkie fingers can be a symptom of many conditions, but carpal tunnel syndrome probably isn't one of them. The carpal tunnel only affects the thumb and first three fingers of your hand, so unless you're experiencing symptoms in the other fingers, look to other conditions that may be causing the problem. Always consult a doctor about any severe pain or stiffness in your joints.
Breaks and Fractures
It may be possible to break, sprain or fracture the small bones of your pinkie finger and not realize it right away. If your finger is stiff or stuck in one position and painful to move, an injury has likely occurred. See a doctor if you suspect a break or fracture. Treatments include immobilization and "fracture reduction," or returning misaligned bones to their proper position--a procedure that may require pain medication or sedation depending on the severity of the injury.
If your pinkie fingers aren't the only area in which you're feeling stiffness, you could be developing osteoarthritis. The symptoms of this degenerative condition--including joint pain, tenderness, loss of flexibility and grating sensations--start small and worsen over time. Pain relievers and physical therapy can ease the symptoms, and surgical options such as joint replacement are sometimes used in severe cases, but there's no known cure.
Stiff pinkie fingers could be a symptom of rheumatoid arthritis, an inflammatory disorder that usually targets your smaller hand and foot joints. Rheumatoid arthritis is different from osteoarthritis; instead of causing extra wear and tear on your joints, it causes swelling in the joint lining, which can lead to bone erosion and joint deformity if left untreated. Other symptoms include fevers, fatigue, red or puffy hands, and bumps on the skin under your arms. There's no cure for rheumatoid arthritis, but treatment options include pain medications, steroids, immune-system suppressors, physical therapy and surgery.
Trigger finger is most common in the middle and ring fingers or thumbs, but it may be possible to develop it in the pinkie finger. The condition occurs when the sheath surrounding the tendon in your finger narrows. If you perform repeated gripping motions in your work or hobbies, trigger finger may result. It can also be caused by rheumatoid arthritis or diabetes. In addition to stiffness, symptoms include popping or clicking noises when moving the finger and the joints "catching" in a bent position, only to pop straight suddenly. Resting the finger and avoiding the motions that caused the condition can cure the condition, along with splinting and finger exercises.