A torn tendon typically announces itself with a combination of immediate, sharp pain, a noticeable loss of strength in the affected limb, and often an audible “pop” at the moment of injury. The more of these signs you experience together, the more likely you’re dealing with a tear rather than a strain or sprain. Here’s how to read your body’s signals and understand what comes next.
What a Tendon Tear Feels Like
The most telling sign is what happens in the first few seconds. Many people hear or feel a distinct pop or snap at the injury site. Orthopedic surgeon Joseph Park at UVA Health notes that patients commonly describe the sensation as feeling like they were shot. That immediate, intense pain is followed by difficulty using the affected body part: you can’t push off your foot, straighten your knee, or lift your arm the way you normally would.
Within minutes, you’ll notice swelling beginning around the injury. Bruising tends to develop over the next day or two as blood from damaged tissue spreads beneath the skin. The inflammatory response peaks around 48 hours after injury, which is when swelling and discoloration are usually at their worst.
Grades of Tendon Injury
Not every tendon injury is a complete rupture. Tendon tears fall on a spectrum from mild to severe, and the grade changes both what you feel and what needs to happen next.
- Grade 1 (mild): Less than 10% of tendon fibers are damaged. You’ll have localized pain that gets worse with movement, mild swelling, and minor loss of function, perhaps less than 5%. The tendon is intact but irritated.
- Grade 2 (moderate): Between 10% and 50% of fibers are torn. Pain is more significant, swelling and bruising are moderate, and you lose roughly 5% to 50% of normal function. The tendon is partially torn but not completely separated.
- Grade 3 (severe): More than 50% of fibers are disrupted, up to a complete tear. Pain is severe, swelling and bruising are extensive, and you may be able to feel a gap or defect where the tendon should be. Loss of function is dramatic, often total for the movement that tendon controls.
Visible Signs You Can Check
Some tendon tears produce changes you can see. A complete biceps tendon rupture, for example, causes the muscle belly to bunch up into a rounded lump in the upper arm, a deformity sometimes called “Popeye sign” because it resembles an exaggerated bicep bulge. This lump becomes more obvious when you try to flex your elbow. If you see an unusual bulge in your arm after an injury, that’s a strong visual indicator of a rupture.
For knee tendons, the position of your kneecap can shift. A torn quadriceps tendon (above the kneecap) can pull the kneecap lower than normal, while a torn patellar tendon (below the kneecap) lets it ride higher. Comparing your injured knee to the other side can reveal asymmetry. In the Achilles tendon area, a visible dip or indentation above the heel where the tendon should feel firm and continuous suggests a rupture.
Testing Strength and Movement
The most reliable thing you can do at home is test whether the injured area can still perform its primary job. Tendons connect muscle to bone, so when one tears, the muscle loses its anchor and can no longer move the joint properly. Each location has its own telltale movement loss.
For the Achilles tendon, try standing on your toes on the injured side. If you can’t rise up on the ball of your foot or push off while walking, that strongly suggests a rupture. A clinical version of this, called the Thompson test, involves lying face down and having someone squeeze your calf muscle. If the foot doesn’t move downward when the calf is squeezed, the Achilles is likely torn.
For the knee, try to straighten your leg while sitting on the edge of a bed. If you can’t extend your knee against gravity or lift your leg straight while lying down, the quadriceps or patellar tendon may be ruptured.
For a distal biceps tear (at the elbow), the giveaway is weakness when rotating your palm upward, like turning a doorknob or a screwdriver. This motion, called supination, loses roughly 60% of its strength after a complete distal biceps rupture. You’ll also notice weakness when bending your elbow against resistance. If twisting and lifting feel dramatically weaker on one side, that points to a tear rather than a simple strain.
How a Torn Tendon Differs From a Sprain
Sprains injure ligaments (which connect bone to bone), while tendon tears damage the connection between muscle and bone. The practical difference: a sprain causes joint instability and pain with movement, but you can usually still contract the muscle. A torn tendon removes your ability to perform a specific motion altogether. If you can tighten the muscle but the joint doesn’t move the way it should, the tendon is the likely problem.
Pain location also helps. Tendon tears hurt where the muscle meets bone, often at the end of a limb or near a joint. The pain tends to be sharp and specific at the moment of injury, then transitions into a deep ache with any attempt to use the muscle. Sprains produce more diffuse pain around the joint itself.
How Tears Are Confirmed
A physical exam catches most complete tendon ruptures, but imaging confirms the diagnosis and reveals partial tears that can be harder to detect by feel alone. The two main options are ultrasound and MRI.
MRI is the gold standard. In studies comparing both methods against surgical findings, MRI detected tendon tears with 100% sensitivity and 100% specificity. Ultrasound came close, with 88% sensitivity and 100% specificity, missing only a small number of partial longitudinal tears. Ultrasound has the advantage of being faster, cheaper, and available in many offices during a first visit. Your provider will choose based on what’s available and how much detail is needed.
Why Timing Matters
If your symptoms point toward a complete tear, getting evaluated quickly makes a real difference in outcomes. The surgical repair window varies by location, but it’s measured in days, not months.
Quadriceps and patellar tendon repairs produce better results when performed within one week of injury. Biceps tendon tears at the shoulder should ideally be repaired within two weeks if surgery is the chosen route. Distal biceps tears at the elbow need prompt evaluation because surgical repair is the most common approach and delays can complicate the procedure.
The two biggest mistakes in the initial evaluation, according to the American College of Emergency Physicians, are failing to test active range of motion and failing to test strength against resistance. If you’re being assessed for a possible tear, make sure your provider watches you try to move the joint on your own and pushes back against your movement. Passive flexibility (someone else moving your joint) can seem normal even with a complete rupture, which is why active testing is essential.