A dislocated thumb occurs when the bones forming one of the thumb’s joints separate from their normal alignment. The thumb has two main joints susceptible to this injury: the metacarpophalangeal (MCP) joint (the knuckle closest to the palm) and the interphalangeal (IP) joint (nearer the tip). This injury is typically caused by sudden, forceful hyperextension, such as falling onto an outstretched hand or receiving high-impact trauma common in sports. The force displaces the joint surfaces, often tearing the stabilizing ligaments and the volar plate, a thick ligament on the joint’s palmar side.
Recognizing the Injury and Immediate Stabilization
A dislocated thumb causes immediate, sharp pain accompanied by noticeable swelling and bruising around the affected joint. The most definitive sign is a visible deformity, where the thumb appears crooked or bent at an unnatural angle, and the joint’s normal contour is lost. Movement becomes severely limited or impossible, and nerve compression can lead to numbness or a tingling sensation in the digit.
The immediate priority is stabilization and managing the initial trauma before professional medical help is sought. The principles of Rest, Ice, Compression, and Elevation (R.I.C.E.) should be applied, starting with resting the hand and avoiding movement of the injured thumb. An ice pack wrapped in a cloth should be applied for 10 to 20 minutes at a time to minimize swelling and pain during the initial 24 to 48 hours.
The entire hand should be kept elevated above the level of the heart, such as by propping it on a pillow. This uses gravity to reduce fluid accumulation and swelling.
Never attempt to “pop” the thumb back into place, as this manipulation can cause severe secondary damage. Self-reduction attempts risk tearing tendons, nerves, or blood vessels. This can convert a simple dislocation into a complex one that is much harder for a physician to treat.
Professional Medical Procedures for Reduction
Diagnosis is confirmed through X-rays, which visualize the joint’s displacement and check for associated fractures, such as an avulsion fracture where a ligament pulls a bone fragment away. Before realignment, the area requires pain management, typically using a regional nerve block. This involves injecting an anesthetic like lidocaine near the median and radial nerves at the wrist, temporarily paralyzing the muscles, easing pain, and allowing for a gentler procedure.
The most common treatment is a closed reduction, where the physician manually manipulates the bones back into their proper position. For frequent dorsal dislocations, the technique involves gently hyperextending the thumb to disengage the joint surfaces, then applying downward pressure on the proximal bone while simultaneously flexing the joint. The physician must avoid pulling with simple longitudinal traction, which can inadvertently trap soft tissues like the volar plate inside the joint, preventing reduction.
If closed reduction fails, the injury is classified as a complex dislocation, requiring open reduction surgery. This intervention is necessary when soft tissues—most commonly the volar plate, sesamoid bones, or flexor tendons—become trapped between the joint surfaces, a condition often called “locked thumb syndrome.” Surgery allows the orthopedic specialist to directly visualize and remove the trapped tissue. The specialist can then repair any torn ligaments and stabilize the joint, sometimes using temporary Kirschner wires (K-wires).
Recovery, Rehabilitation, and Preventing Reinjury
Following a successful reduction, the thumb is immobilized in a protective device, most commonly a short-arm thumb spica splint or cast. Immobilization is maintained for three to four weeks to allow the damaged ligaments and joint capsule to begin healing. Prolonged immobilization beyond this period is avoided because it can lead to significant joint stiffness and loss of mobility.
Physical therapy (PT) is initiated to restore the hand’s full function, focusing on regaining range of motion and building strength. The early phase involves gentle active range-of-motion exercises, such as isolated flexion of the MCP and IP joints and finger-to-thumb opposition movements. As healing progresses, the intermediate phase introduces light strengthening exercises, often using therapy putty or a resistance band to strengthen pinch and grip power.
To prevent recurrence, continued strengthening of the surrounding musculature is advised, especially for athletes. Muscle stability reduces reliance on the damaged ligaments. Protective taping is a common preventative measure, using rigid sports tape to create a supportive sling around the wrist and the MCP joint, resisting the hyperextension force that caused the initial injury. This provides external support during activity while internal structures regain stability.