## **Core Concept**
The condition described is suggestive of **trigger finger**, also known as **stenosing tenosynovitis**. It occurs when the tendon sheath that surrounds the tendon becomes inflamed and narrowed, causing the finger to lock in a flexed position. This condition can be associated with diabetes.

## **Why the Correct Answer is Right**
The first line treatment for trigger finger often involves conservative measures before considering surgical intervention. **Steroid injections** into the tendon sheath are a common first-line treatment. They help reduce inflammation and can often resolve the condition. The mechanism involves the anti-inflammatory effects of steroids, which can help in reducing the swelling of the tendon sheath and thus alleviate the symptoms.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While **NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)** can help manage pain and inflammation, they are generally considered less effective than steroid injections for directly addressing the mechanical issue of a locked finger.
- **Option B:** **Physical therapy** and exercises might be recommended alongside other treatments but are not typically considered the first line of treatment for acute trigger finger, especially when the condition significantly interferes with hand function.
- **Option C:** This option is not provided, but typically, surgical release would be considered if conservative measures like steroid injections fail.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **steroid injections** are often very effective for trigger finger and can be both diagnostic and therapeutic. Patients should be informed that after the injection, the symptoms might temporarily worsen before improving.

## **Correct Answer:** D. Steroid injection.