**Question:** Which of the following solutions is recommended for TMJ (temporomandibular joint) arthrocentesis:

A. Normal saline
B. Lidocaine with adrenaline
C. Glycerol
D. Chlorhexidine

**Core Concept:** TMJ arthrocentesis is a procedure involving the removal of joint fluid, commonly performed to diagnose and manage temporomandibular joint disorders (TMDs). The solution used should be sterile, non-irritating, and compatible with joint tissues.

**Why the Correct Answer is Right:** The recommended solution for TMJ arthrocentesis is **Normal saline (A)**. Normal saline is a sterile, isotonic solution that maintains osmotic balance and minimizes tissue irritation during the procedure. It is commonly used as it does not interfere with joint biochemistry and is easily available.

**Why Each Wrong Option is Incorrect:**

**Option B (Lidocaine with adrenaline):** Lidocaine is a local anesthetic and adrenaline is a vasoconstrictor. While they may be useful for anesthesia during the procedure, they can cause tissue toxicity and alter joint fluid properties, making them unsuitable for arthrocentesis.

**Option C (Glycerol):** Glycerol is a hypertonic solution and can cause oedema, inflammation, and tissue damage upon direct contact with joint structures. It is not recommended for TMJ arthrocentesis.

**Option D (Chlorhexidine):** Chlorhexidine is an antiseptic agent used for skin preparation, not suitable for TMJ arthrocentesis due to its hypertonic nature and potential tissue toxicity.

**Clinical Pearl:** Arthrocentesis should be performed gently, with minimal pressure to reduce complications and ensure accurate diagnostic results. The procedure is usually performed under ultrasound guidance to improve accuracy and reduce complications.