The Flexor Carpi Radialis (FCR) is a muscle of the forearm essential for movements of the hand and wrist. This long, slender muscle provides the fine motor control and power necessary for everyday actions. It is located in the superficial group of muscles on the anterior, or palm-facing, side of the forearm.
Locating the Flexor Carpi Radialis
The FCR is situated in the superficial layer of the anterior compartment of the forearm, easily accessible just beneath the skin. It originates at the medial epicondyle of the humerus, a bony knob on the inner side of the elbow, an origin shared with several other forearm flexor muscles.
From the elbow, the muscle travels diagonally down the forearm toward the thumb side of the wrist. Roughly halfway down, the muscle belly transitions into a long, strong tendon that crosses the wrist joint.
The tendon’s insertion is primarily at the base of the second metacarpal bone (index finger). A smaller portion may also attach to the base of the third metacarpal bone (middle finger). This diagonal course gives the muscle its characteristic dual function. The tendon passes through its own small tunnel near the wrist, separate from the main carpal tunnel.
The Primary Actions of the FCR
The FCR performs two main actions at the wrist joint, resulting from its diagonal position across the forearm. Its primary function is wrist flexion, which is the action of bending the hand forward toward the palm side of the forearm. This movement is a fundamental component of gripping and pulling activities.
The muscle’s secondary action is radial deviation, also known as wrist abduction. This movement shifts the hand laterally toward the thumb side of the forearm. This side-to-side motion is crucial for fine-tuning the hand’s position when manipulating objects or using tools.
The dual nature of the FCR’s action arises because its path is angled toward the radius, the bone on the thumb side. When the muscle contracts, it pulls the hand toward the forearm (flexion) and toward the thumb side (radial deviation) simultaneously. The FCR is innervated by the median nerve, which provides the electrical signal necessary for the muscle to contract.
Common Issues and Management
The FCR tendon is susceptible to an overuse injury known as Flexor Carpi Radialis Tendinitis, which causes pain on the palm side of the wrist near the base of the thumb. This inflammation occurs where the tendon passes through its narrow tunnel, often due to repetitive strain or a sudden increase in activity.
People who engage in sports requiring repetitive wrist movements, such as golf or racquet sports, or those with jobs involving heavy gripping are at higher risk. Symptoms include localized pain and tenderness when pressing on the tendon, particularly just below the wrist crease.
The pain often worsens with motions that stress the tendon, like bending the wrist toward the palm and thumb against resistance. FCR tendinitis is often confused with other sources of radial wrist pain, such as arthritis or De Quervain’s tenosynovitis, making correct diagnosis important.
Initial treatment focuses on conservative management to reduce inflammation and allow the tendon to heal. This typically involves resting the wrist and modifying activities that provoke the pain, sometimes by avoiding lifting with the palm facing upward.
Using a wrist splint to keep the wrist in a neutral or slightly bent position for a few weeks can help by reducing tension on the tendon. Non-surgical approaches also include applying cold packs and using non-steroidal anti-inflammatory medications to manage swelling and discomfort.
Physical therapy is often recommended to introduce gentle stretching and tendon-gliding exercises, followed by gradual strengthening. Most individuals regain full function with this conservative approach, though severe cases may require a corticosteroid injection or, rarely, surgical intervention.