What is a Sprained Thumb?
A sprained thumb is a relatively common condition characterized by damage or tearing of the connective tissue (such as ligaments, cartilage and joint capsule) of the thumb.
The thumb comprises of 2 small bones known as phalanges. These small bones join to each other at the IP joint (Interphalangeal Joint) and to the bone at the thumb side of the palm (1st metacarpal) at the MCP joint (Metacarpophalangeal Joint) forming 2 joints for the thumb (figure 1). Each of these joints comprise of strong connective tissue wrapping around the bony ends and cartilage, which lies between the joint surfaces, cushioning the impact of one bone on another during activity.
Figure 1 - Relevant Anatomy for a Sprained Thumb
During certain movements of the thumb, stretching or compression forces are placed on the thumb joints. If these forces are excessive due to too much repetition or high force, injury to the joints may occur. This may involve damage to the cartilage or tearing to the connective tissue surrounding the joint (such as ligaments or joint capsule). When this occurs, the condition is known as a sprained thumb and may affect the IP or MCP joint.
Causes of a Sprained Thumb:
Sprained thumbs are extremely common in ball sports, such as basketball or netball, and frequently occur due to a specific incident, such as a hyperextension force (backward bending of the thumb), hyperflexion force (excessive forward bending of the thumb) or a sideways force. A sprained thumb may also occur in contact sports due to a collision with another player or when tackling, or in martial arts (e.g. blocking a punch or kick with the thumb). A thumb sprain also commonly occurs in skiing when one of the hand poles forces the thumb backwards during an awkward landing or fall.
Occasionally, a sprained thumb may occur due to repetitive strain associated with overuse. This may be the case in patients who perform repetitive activities involving end of range movements of the thumb.
Signs and Symptoms of a Sprained Thumb:
Patients with a thumb sprain often experience a sudden onset of thumb pain during the causative activity. However, patients may also experience pain and stiffness after the provocative activity with rest (particularly at night or upon waking the following morning). Symptoms may be felt on the front, back or sides of the affected thumb joint and occasionally pain may be referred into the hand or wrist on the affected side. There may be an audible snap or pop sound at the time of injury. Swelling, bruising or colour change (such as redness) will often develop around the affected joint. Symptoms are generally exacerbated with activities that involve use of the hand, fingers and thumb such as catching balls, knocking the thumb, opening jars or doors, writing, picking up heavy objects, texting on a mobile phone, general gripping activity, cooking, household activities or placing weight through the affected hand and thumb.
It is also common for patients to experience pain on firmly touching the affected region, and, in some cases, a feeling of weakness in the hand and thumb may also be present. In severe cases, the thumb may be completely dislocated. All thumb dislocations need to be managed by a medical professional and should be X-rayed before and after being put back into place to confirm relocation and to exclude fracture.