Tendonitis produces a recognizable pattern: a dull ache right where the tendon meets the bone, tenderness when you press on the area, and mild swelling that worsens with movement. You can check for these signs yourself with some simple hands-on tests, and the location of your pain will tell you a lot about which tendon is involved. Here’s how to evaluate what’s going on before deciding on next steps.
The Three Core Signs
Tendonitis consistently shows up with the same trio of symptoms regardless of location. First, you’ll notice a dull ache that flares when you move the affected joint or limb. It’s not a sharp, sudden pain (that points to something else). Second, the area will be tender to the touch, meaning pressing on the tendon itself reproduces or intensifies the pain. Third, you may see or feel mild swelling or tightness around the tendon.
A useful starting test: press firmly along the tendon with your fingertip, moving slowly from the muscle toward the bone where it attaches. If you find a specific spot that hurts significantly more than the tissue around it, that’s a strong indicator. Then try using the joint against light resistance. If resisted movement hurts but passive stretching hurts less, you’re likely dealing with an irritated tendon rather than a joint problem.
Checking by Location
Outer Elbow (Tennis Elbow)
Lateral epicondylitis is the single most common form of tendonitis, with an incidence nearly three times higher than the next most frequent type. It peaks between ages 40 and 59 and affects women more often than men. You’ll feel pain on the bony bump on the outside of your elbow.
To test it at home, sit in a chair and bend your elbow to 90 degrees with your palm facing down. Now try to extend your wrist upward while pressing down on the back of your hand with your other hand, creating resistance. If this reproduces pain right at that outer elbow bump, that’s a positive result. You can also try this: with your arm straight out and palm facing down, have someone gently push your wrist into flexion (bending it downward) while you resist. Pain at the outer elbow again points to tennis elbow. These are simplified versions of clinical tests called Cozen’s and Mill’s tests.
Achilles Tendon
Achilles tendonitis typically shows up 2 to 6 centimeters above the heel bone, in the middle or upper portion of the tendon. Squeeze the tendon gently between your thumb and forefinger and slide along its length. You may feel thickening, a small nodule, or a section that’s noticeably more tender than the rest.
Here’s a more specific check: while seated, slowly point your toes down and then pull them up toward your shin. If you feel a bump or swollen area on the tendon that moves along with your foot as you flex, that suggests the problem is within the tendon itself. If the tender spot stays fixed in one place while the tendon slides underneath, the inflammation may be in the sheath surrounding the tendon rather than the tendon itself. Both need attention, but the distinction helps a clinician plan treatment. Achilles tendonitis is most common in people aged 50 to 59 and affects men and women at similar rates.
Knee (Jumper’s Knee)
Patellar tendonitis causes pain at the bottom tip of the kneecap, where the patellar tendon originates. To check, sit on a chair with your leg relaxed and fully extended. Press directly on the lowest point of your kneecap. Tenderness here, especially when the thigh muscles are relaxed, is the hallmark sign. The pain tends to decrease or shift when you bend the knee and tighten the quadriceps, because the tension pulls the tendon taut and makes it harder to press into. This condition is more common in younger, active people compared to most other forms of tendonitis.
Shoulder and Biceps
Rotator cuff and biceps tendonitis both peak after age 40. For the rotator cuff, try raising your arm out to the side. Pain between 60 and 120 degrees of elevation, sometimes called a “painful arc,” suggests tendon irritation. For biceps tendonitis, press into the front of your shoulder, in the groove between the two bony prominences at the top of the arm. Tenderness there, especially when you try to bend your elbow or rotate your forearm against resistance, is a telling sign.
Tendonitis vs. Tendinosis
If your symptoms have dragged on for weeks or months, you may not have tendonitis at all. Tendonitis is acute inflammation of the tendon, with swelling, warmth, and a dull ache that worsens with activity. Tendinosis is a chronic degenerative condition where the tendon’s collagen fibers have started to break down. The tendon becomes thick, hard, and scarred.
The signs differ in subtle ways. Tendonitis produces swelling and tightness that responds to rest and anti-inflammatory measures. Tendinosis causes pain, stiffness, and a burning sensation, often with decreased range of motion and sometimes a firm lump you can feel in the tendon. Tendinosis won’t improve with the same rest-and-ice approach that works for acute tendonitis. An ultrasound can distinguish between the two: it easily picks up the swelling of tendonitis and can also flag the structural changes of tendinosis.
When It Might Be Something Worse
Tendonitis doesn’t produce sudden, dramatic symptoms. If you heard or felt a snap or pop during activity, followed by severe pain, rapid bruising, obvious weakness, or an inability to use the limb or bear weight, that pattern suggests a tendon rupture rather than simple inflammation. A visible deformity or gap where the tendon should be is another red flag. A rupture needs urgent medical evaluation.
Bursitis can mimic tendonitis because the fluid-filled cushions (bursae) near tendons often become inflamed alongside them. The key difference: bursitis pain tends to be more diffuse and aching over a broader area, while tendonitis pain is pinpointed right along the tendon or at its attachment to bone. Pressing directly on the tendon versus the surrounding area can help you tell them apart.
Getting a Professional Diagnosis
A clinician will run through the same palpation and resistance tests described above, plus some additional maneuvers specific to your location. If there’s any question about the diagnosis, imaging can confirm it. Both ultrasound and MRI are highly accurate for detecting tendon problems, with sensitivity around 95% and specificity of 100% in comparative studies. Ultrasound is typically the first choice because it’s faster, cheaper, and lets the clinician watch the tendon move in real time. MRI is reserved for cases where more detail is needed or the diagnosis remains unclear.
Most tendonitis can be identified reliably through physical examination alone. Imaging becomes more important when symptoms have lasted longer than a few weeks, when there’s concern about a partial tear, or when the distinction between tendonitis and tendinosis would change the treatment approach.