Skier’s thumb is a sprain or tear of the ligament on the inner side of your thumb, and treatment depends entirely on how severe the tear is. A partial tear typically heals with four to six weeks of immobilization in a cast or splint, while a complete tear often requires surgery to reattach the ligament. Getting the right treatment early matters: left untreated, this injury carries a serious risk of chronic instability that can permanently weaken your grip.
What Happens Inside the Thumb
The ulnar collateral ligament (UCL) connects the bones at the base joint of your thumb and keeps the thumb stable when you grip, pinch, or push against objects. In skier’s thumb, a forceful bending of the thumb away from the hand stretches or tears that ligament. The classic scenario is a skier falling with a pole still strapped to their hand. The pole catches the ground while momentum drives the thumb backward and outward against the handle. But the same injury happens in ball sports, falls onto an outstretched hand, or any impact that wrenches the thumb sideways.
You’ll feel pain and swelling along the inner edge of your thumb, especially when you try to extend or spread the thumb. Gripping anything, even loosely, often hurts. Bruising may develop over a day or two, and the joint can feel wobbly or weak if the ligament is significantly torn.
How the Injury Is Graded
A clinician will perform a valgus stress test, gently pushing the thumb sideways to check how much the joint opens compared to your uninjured hand. To isolate the ligament, they’ll bend the thumb joint to about 45 degrees before applying pressure. The degree of looseness determines your grade:
- Grade 1 (mild sprain): The ligament is stretched but intact. The joint opens slightly but has a firm stopping point.
- Grade 2 (partial tear): The joint opens more than 15 to 20 degrees beyond normal, but there’s still a definite endpoint when stressed.
- Grade 3 (complete tear): The joint opens 30 to 35 degrees, or more than 15 degrees wider than the other thumb, with no firm endpoint at all.
X-rays are usually taken to rule out a fracture at the base of the thumb bone, since a small chip of bone sometimes pulls off with the ligament. MRI is the most accurate way to confirm the extent of the tear, with close to 100% sensitivity, though it isn’t always needed for straightforward cases. Ultrasound can also assess the ligament in real time and is sometimes done during the initial visit.
Why a Stener Lesion Changes Everything
In some complete tears, the torn end of the ligament flips over a layer of muscle tissue near the thumb and gets trapped on the wrong side of it. This is called a Stener lesion. The muscle tissue sits between the two torn ends like a wall, physically blocking them from reconnecting. No amount of splinting or rest will allow healing when this happens, because the ligament ends simply cannot reach each other. A Stener lesion always requires surgery.
MRI or ultrasound can identify a Stener lesion before surgery. If you have a complete tear and your clinician suspects displaced ligament ends, imaging is important for planning the right treatment.
Treating Partial Tears Without Surgery
If your thumb joint is stable during stress testing, meaning the ligament is partially torn but still holding, immobilization alone is usually enough. Treatment follows a predictable timeline:
For the first four weeks, your thumb is placed in a cast or a custom thermoplastic splint. The thumb is positioned in slight flexion with the base joint immobilized, while the tip joint of the thumb is left free to move. This protects the ligament while preventing unnecessary stiffness.
After four weeks, you transition to a removable splint for about two more weeks. During this period, you begin gentle range-of-motion exercises. Some clinicians use a shorter three-week cast period if the joint is stable in extension, followed by the same transition to a removable splint.
Throughout this process, the key is protecting the thumb from any sideways stress while gradually restoring movement. Most people with partial tears recover full function without surgery.
When Surgery Is Needed
Surgery is recommended for Grade 3 injuries where the joint opens more than 30 to 35 degrees, or shows more than 15 degrees of looseness compared to the other thumb. It’s also required whenever a Stener lesion is present.
The procedure reattaches the torn ligament to the bone at the base of your thumb. Surgeons typically use small anchors embedded in the bone with sutures threaded through the ligament to pull it back into position. An older technique involves drilling small tunnels through the bone and threading sutures through them to secure the ligament. Both approaches achieve the same goal: restoring the ligament to its original attachment point so it can heal in place.
Outcomes after surgical repair are consistently strong. Across multiple studies, grip strength after recovery averages around 97% of the uninjured hand, and pinch strength recovers to over 90%. Patient satisfaction rates range from 72% to 92% reporting near-normal thumb function, with some studies showing all participants satisfied with their result.
Recovery Timeline After Surgery
Post-surgical recovery mirrors the conservative timeline in the early weeks but takes longer overall. Your thumb goes into a cast for four weeks immediately after surgery. After that, you switch to a removable splint for roughly two more weeks and begin active range-of-motion exercises under guidance.
The critical restriction is avoiding any activity that stresses the ligament for three to four months after surgery. That means no gripping heavy objects, no sports involving the hands, and no forceful pinching. This is the window the ligament needs to fully heal and regain its structural strength. Returning to activity too early risks re-tearing the repair.
Rehabilitation Exercises
Once your clinician clears you for exercises, typically around the six-week mark, you’ll start with gentle bending movements. Each exercise should be done slowly, stopping if you feel pain.
The first exercise targets the tip joint of your thumb. Rest your forearm on a table with the thumb pointing up, hold the thumb steady just below the joint nearest your nail, and bend only the tip down and back up. Repeat 8 to 12 times. The second exercise works the base joint: hold the base of your thumb and palm steady with your other hand, then bend the thumb downward where it meets your palm and straighten it. Same 8 to 12 repetitions.
These exercises focus on restoring isolated movement at each joint without putting sideways stress on the healing ligament. Strengthening exercises, like pinching putty or squeezing a soft ball, come later in recovery once the ligament has had time to fully heal. Your therapist will progress you based on how the joint feels and how much motion you’ve regained.
What Happens If You Skip Treatment
An untreated complete UCL tear leads to chronic instability at the thumb’s base joint. Over time, the joint wobbles during everyday tasks like turning a key, opening a jar, or writing. The persistent instability accelerates wear on the joint surfaces, eventually causing arthritis. At that point, treatment becomes more complex. Instead of a straightforward ligament repair, you may need a ligament reconstruction using tissue from elsewhere in the hand, or in advanced cases, a joint fusion that sacrifices movement to restore stability. Early treatment, whether a splint for partial tears or surgery for complete ones, prevents this progression.