A tendon is a strong, cord-like structure made primarily of collagen that connects muscle to bone. When a muscle contracts, it pulls on the attached tendon, which then pulls on the bone to create movement at a joint. A complete cut, or laceration, immediately disrupts this functional connection. Because the tendon is under constant tension from the muscle, a severed tendon results in the ends snapping apart and retracting, leaving a gap that cannot heal on its own. This type of injury is severe, causing an immediate loss of function, and requires prompt professional medical attention.
Understanding the Function of Tendons
Tendons are integral to the musculoskeletal system, translating the energy of a muscle into skeletal motion. When a muscle contracts, the tendon transmits that pulling force to the bone, enabling a wide range of movements from walking to intricate finger actions. Tendons are strong and resistant to tearing, but they are not highly elastic, which is why a sudden, sharp force can cause them to snap.
Tendons are found throughout the body wherever muscle meets bone, but those in the hands, wrists, and ankles are particularly vulnerable to lacerations due to their superficial location. Flexor tendons allow you to bend your fingers and make a fist, while extensor tendons allow you to straighten them. Damage to either type severely impairs the use of the hand.
Immediate Physical Consequences of a Severed Tendon
The most immediate and dramatic consequence of a completely severed tendon is the functional loss of movement in the affected joint. Since the connection between the muscle and bone is broken, the muscle can no longer pull on the bone, making it impossible to actively bend or straighten the joint controlled by that tendon. For example, a severed flexor tendon in the finger will prevent the person from actively bending that finger into a fist.
Acute symptoms include severe pain at the moment of injury, followed by rapid swelling and often significant bleeding, depending on the depth of the wound. A characteristic sign of a complete tendon cut is the retraction of the two severed ends due to the constant pull of the associated muscle. This retraction creates a space, or gap, between the ends, which is why the body cannot simply heal the injury without intervention.
The patient may hear or feel a distinct “snap” or “pop” at the time the tendon is cut or ruptured. Because nerves and blood vessels often run very close to tendons, a deep laceration frequently causes associated damage to these structures. This combined injury can lead to numbness in the affected area and, in severe cases, compromise the blood supply to the limb.
Surgical Repair and Medical Management
The standard medical management for a severed tendon is a surgical procedure known as tenorrhaphy, which involves suturing the two ends back together. This operation is often considered an emergency procedure to prevent further retraction of the tendon ends and to allow for the best chance of a successful outcome. During surgery, the surgeon must first locate the retracted tendon ends, which can sometimes be far from the original site of the cut.
The two ends are meticulously aligned and then sutured together using specialized, strong stitching techniques. Achieving the correct tension in the repaired tendon is a delicate process, as too much tension can cause the sutures to fail, while too little can result in a functionally weak tendon. The goal is to create a repair strong enough to withstand the forces of early mobilization while the biological healing process begins.
Following the repair, the injured area is immobilized using a splint or cast to protect the delicate sutures from being pulled apart. This period of immobilization is mandatory to allow the initial healing phase to establish a bond between the tendon ends. Post-operative care also focuses on controlling swelling through elevation and managing pain with prescribed medication.
Rehabilitation and Functional Recovery
Tendon healing follows a predictable biological sequence involving the inflammatory, proliferative (repair), and remodeling stages. The inflammatory phase begins immediately and lasts for about a week, focusing on managing swelling and initiating the repair process. During the proliferative stage, which spans the next few weeks, the body generates new collagen fibers to bridge the gap, but the repair remains fragile.
Physical therapy (PT) or occupational therapy is a mandatory component of recovery, often beginning within days or weeks of the surgery. The therapist supervises controlled, protected motion exercises to prevent scar tissue from forming restrictive adhesions between the repaired tendon and surrounding tissues. Early controlled movement is crucial for guiding the collagen fibers to align correctly and for restoring the tendon’s ability to glide smoothly.
The final remodeling phase can last from several months up to a year, as the newly formed collagen matures and gains tensile strength. Full functional return, including a return to sports or heavy manual labor, is a gradual process that may take six to twelve months, depending on the tendon and the complexity of the injury. While many individuals regain excellent function, some may experience residual stiffness or a minor reduction in grip strength or range of motion due to the initial injury and subsequent scar tissue formation.