MCP Thumb Injury

The ulnar collateral ligament links to the MCL (metacarpophalangeal) joint at the bottom of the thumb at the point where the thumb is attached to the hand. Injury to this band of tissue affects the MCP joint and can often result from a forceful outward yank or other pressure on the thumb.

Symptoms of MCP Thumb Injury

The MCP joint at the bottom of the thumb will be painful and is likely to become inflamed. The thumb may feel frail or weakened during movements such as grasping and pinching, plus holding objects can become difficult, especially clutching things between forefinger and thumb. The area around the injury can become bruised or discoloured. Due to the nature of the injury, which involves tearing of the associated ligament, the loose portion of this ligament can often be felt as a bump on the edge of the thumb close to the palm.

Causes of MCP Thumb Injury

Excessive force on the thumb, extending it away from the hand, is the main cause of damage to the ulnar collateral ligament and the resulting MCP injury. The injury is sometimes known as 'skier's thumb' because the injury is regularly provoked when a skier falls onto their hand while holding their ski pole, causing the thumb to bend outwards. This can potentially occur after any fall onto the palm, particularly in a bat or racquet sport when holding something that can push back the thumb. The thumb's outward bending is called a valgus force and can tear or even rupture the associated ligament. Repetitive actions involving valgus force can also contribute to ligament damage over time.

Medical Treatment for MCP Thumb Injury

A doctor will conduct a physical examination on both hands and will take an x-ray and any other suitable tests to assess the exact nature of the injury and the damage. Some ligament damage might not show up on an x-ray. A valgus stress test may be used in order to test the ligament and stability of the joint; this will involve carefully moving the thumb into many positions, with an anaesthetic sometimes administered beforehand. The steadier the joint, the less severe the ligament damage is likely to be. In this case the doctor can recommend suitable conservative treatment, such as immobilising the thumb for 4 to 6 weeks followed by a course of exercises designed to help strengthen grip and improve motion in the thumb. Normal activity is usually resumed within another month.

Surgery for MCP Thumb Injury

However, an unstable joint can point to a total rupture and this might require surgery because the ligament will not be able to heal correctly. This involves looking for any signs of soft tissue damage and repairing the torn ligament and attaching it to the bone. Surgery is mostly successful and thumb movement and strength should return with time and exercise. In rare instances there can be numbness on the back of the thumb due to damage to nerves, but in this eventuality the numbness should recover by itself. You can expect to return to normal activity within approximately 3 months.