A sagittal band rupture, commonly known as “boxer’s knuckle,” is an injury to the hand’s connective tissues that stabilize the finger tendons. This condition involves tearing the structures responsible for keeping the extensor tendon centered over the knuckle. When this happens, the tendon can slip out of its groove, causing a noticeable snap or pop and significant functional impairment. Whether the damage can mend itself without surgery depends heavily on the severity of the tear and the stability of the affected joint, requiring careful assessment to determine the appropriate path to recovery.
What Are Sagittal Bands and How Do They Tear?
Sagittal bands are thin, ribbon-like stabilizers that form part of the extensor mechanism on the back of the hand. They originate from the structures surrounding the metacarpophalangeal (MCP) joint, or knuckle joint, and wrap around the extensor tendon. Their primary function is to act like a sling, keeping the extensor tendon precisely aligned over the middle of the knuckle during both finger flexion and extension.
When a sagittal band is compromised, the extensor tendon loses its mooring and can slip sideways, typically to the ulnar side of the knuckle. The most frequent cause of this injury is a direct, forceful impact to the knuckle, such as punching a hard object, which causes the band to tear away from its attachment. This acute trauma generates immediate pain, swelling, and a sensation of the tendon snapping or subluxating when the finger attempts to move. The extent of the tear determines whether the tendon subluxates (slips partially) or fully dislocates.
Non-Operative Treatment: When Self-Healing Is Possible
Self-healing of a sagittal band rupture is possible, but only when the tear is partial and the injury is acute. This non-operative approach is successful when the tendon exhibits minimal or intermittent subluxation. The goal of conservative management is to immobilize the joint to allow the torn tissue to scar and reconnect, restoring the necessary tension to the extensor mechanism.
The standard protocol involves placing the affected finger and knuckle in an extension splint, which holds the MCP joint straight and keeps the extensor tendon centered. This prevents the tendon from slipping out of place, which would otherwise disrupt the healing tissue. Patients must wear this splint continuously for a period of about four to six weeks to give the band sufficient time to consolidate and stabilize the tendon. Rest and anti-inflammatory medication are also components of the initial treatment plan to manage pain and swelling in the acute phase.
The success of non-operative healing hinges on strict adherence to the immobilization schedule prescribed by a healthcare professional. If the tear is more severe or if the tendon continues to slip out of its groove despite splinting, the treatment is likely to fail. When the tendon repeatedly subluxates or dislocates, the mechanical forces acting on the joint prevent the torn ends of the band from forming a strong, lasting scar. If the injury is chronic or the initial splinting fails, surgical intervention becomes the necessary alternative.
Indications for Surgical Repair and Post-Treatment Care
When conservative measures fail to stabilize the extensor tendon, or if the initial injury involves a complete rupture (dislocation), surgical repair is indicated. Chronic injuries, defined as those persisting beyond six weeks, also require surgery because the torn edges of the sagittal band have retracted and are unlikely to heal on their own. Surgery is necessary to prevent the long-term consequences of chronic tendon subluxation, which can include functional loss, pain, and a constant snapping sensation during finger movement.
The surgical procedure aims to repair the torn sagittal band directly or to reconstruct a new stabilizer to centralize the extensor tendon over the knuckle joint. In a direct repair, the surgeon sutures the torn edges of the band back together. Reconstruction may involve using a segment of the extensor tendon itself or other local soft tissue to create a new sling. The ultimate objective is to restore the mechanical stability that prevents the tendon from slipping sideways during gripping or extension.
Post-treatment care begins with a period of immobilization, often lasting about six weeks, to protect the repair. This is followed by controlled mobilization exercises and formal hand therapy under the guidance of a specialist. Rehabilitation is crucial for regaining full range of motion and strength, focusing on specific exercises to ensure the tendon glides smoothly in its newly stabilized position. Full recovery, including the return of pre-injury function, can take five to six months.