Pain on the inside (medial side) of your knee is one of the most common knee complaints, and it usually traces back to one of a handful of structures packed into that area: a ligament, a piece of cartilage, a fluid-filled cushion, or the joint surface itself. The cause depends heavily on how the pain started, your age, and what makes it worse. Here’s how to narrow it down.
What’s on the Inside of Your Knee
The inner side of your knee is a busy intersection of soft tissue. The medial collateral ligament (MCL) runs vertically along the inside, connecting your thighbone to your shinbone and preventing the knee from bending inward. Just inside the joint sits the medial meniscus, a C-shaped wedge of cartilage that acts as a shock absorber between the bones. Below the joint line, three tendons converge and attach to the shinbone at a spot called the pes anserinus, with a small fluid-filled sac (bursa) cushioning them. And the joint surfaces themselves are lined with smooth cartilage that can wear down over time.
Each of these structures produces a slightly different pattern of pain, which is what makes the location, timing, and behavior of your symptoms so useful for figuring out what’s going on.
MCL Sprain or Tear
The MCL is the most commonly injured ligament in the knee. It typically happens during a blow or force that pushes the knee inward, common in contact sports, skiing, or even an awkward step. You’ll feel pain directly along the inner edge of the knee, and there’s often swelling and tenderness right over the ligament.
MCL injuries are graded by severity:
- Grade 1 (mild): Less than 10% of the ligament fibers are torn. The knee still feels stable, and you’ll have tenderness and mild pain. This usually heals within one to three weeks.
- Grade 2 (moderate): The ligament is partially torn. Pain and tenderness are more intense, and the knee may feel loose when moved side to side. Recovery typically takes four to six weeks.
- Grade 3 (severe): A complete tear through both layers of the MCL. The knee feels very unstable, and pain is significant. Healing takes six weeks or longer, and some cases need surgical repair.
A key feature of MCL injuries is that the pain is worst when something pushes the knee inward. If someone were to press on the outside of your knee while your foot was planted, a damaged MCL would protest immediately.
Medial Meniscus Tear
The medial meniscus tears more often than its counterpart on the outer side, partly because it’s less mobile and absorbs more force. In younger people, this usually happens with a twisting injury while the foot is planted. In people over 40, the cartilage can degrade and tear with everyday activity, sometimes without a single memorable event.
Meniscus tears produce a distinct set of symptoms. Pain develops along the joint line, right in the crease of the knee. Swelling often builds gradually over a day or two rather than appearing instantly. The hallmark sign is mechanical catching or locking: a loose piece of torn cartilage can get wedged in the joint, temporarily preventing you from fully straightening your leg. You may also notice the knee giving way or feeling unreliable during activity. Many people with meniscus tears feel more comfortable with the knee slightly bent.
One useful distinction: meniscus pain is felt right at the joint line (the seam between your thighbone and shinbone), while pain from plica syndrome, a less common cause, sits just above it.
Pes Anserine Bursitis
This one is easy to miss because the pain isn’t at the joint line. It sits about two to three inches below the knee on the inner side of the shinbone, where three tendons meet and a bursa cushions them against the bone. When that bursa gets irritated, it swells and produces a localized aching or burning pain.
Pes anserine bursitis is especially common in runners, people with osteoarthritis, and those who are overweight. The pain tends to flare with specific movements: climbing or descending stairs, kneeling, and standing up from a chair. It can also ache at night if you sleep with your knees touching. If your inner knee pain is below the joint and gets worse with stairs, this is a strong candidate.
Osteoarthritis of the Inner Knee
The medial compartment of the knee bears more load than the outer side, which is why osteoarthritis often shows up here first. Over years, the cartilage lining the joint surfaces thins and roughens, eventually allowing bone-on-bone contact. X-rays show this as a narrowing of the space between the bones, along with bone spurs and remodeling.
Osteoarthritis pain is typically worst after prolonged activity or at the end of the day. Morning stiffness is common but usually improves within 20 to 30 minutes of moving around (unlike inflammatory arthritis, where stiffness lasts much longer). The knee may feel achy and stiff after sitting for a while, then loosen up with gentle movement. Over time, you might notice a gradual bowing of the leg inward as the inner compartment loses cartilage height.
This is primarily a condition of people over 50, though prior injuries, excess body weight, and repetitive occupational stress can accelerate it. If your inner knee pain has been building slowly over months or years without a specific injury, osteoarthritis is one of the most likely explanations.
Plica Syndrome
A plica is a fold of tissue left over from fetal development that lines the inside of the knee joint. Most people have one and never know it. But when the medial plica gets irritated from repetitive bending, overuse, or a direct hit, it can thicken and snap over the bony ridge of the thighbone, producing a dull ache on the inner knee.
Plica syndrome is often confused with a meniscus tear because both cause inner knee pain. The distinguishing detail is location: plica pain sits above the joint line, while meniscus pain is right at it. You might also feel a snapping sensation when bending and straightening the knee, and the area can be tender to the touch just above and to the inside of the kneecap.
How to Tell These Apart
The location and behavior of the pain are your best clues before any imaging:
- Pain along the inner edge of the knee, worse with side-to-side stress: likely MCL.
- Pain at the joint line with catching, locking, or giving way: likely meniscus.
- Pain below the joint on the shinbone, worse with stairs and kneeling: likely pes anserine bursitis.
- Gradual, aching stiffness that improves with movement, especially over age 50: likely osteoarthritis.
- Pain above the joint line with a snapping sensation: likely plica syndrome.
Clinicians use specific hands-on tests to confirm suspicions. The McMurray test, which involves rotating and extending the knee while feeling for a click, has a sensitivity around 80 to 91% for meniscus tears. The valgus stress test, which applies inward pressure on the knee, catches MCL tears with 86 to 96% sensitivity. But imaging, particularly MRI, is often needed for a definitive answer, especially when the exam is ambiguous.
What Helps Inner Knee Pain
The right approach depends on the cause, but several strategies overlap across nearly all of these conditions. Reducing the load on the knee through rest from aggravating activities, maintaining a healthy weight, and using ice for acute flare-ups forms the foundation.
Strengthening the muscles around the knee is one of the most effective long-term strategies. The inner portion of the quadriceps muscle, called the VMO, is a key stabilizer of the kneecap and the knee overall. Exercises that target it, like squeezing a ball between the knees or performing shallow wall sits, help distribute forces more evenly across the joint. Strengthening the hip muscles, particularly the ones that control side-to-side stability, also reduces strain on the inner knee by improving how the leg tracks during walking and running.
For MCL sprains, most Grade 1 and 2 injuries heal well with bracing, rest, and progressive rehabilitation. Meniscus tears sometimes settle with physical therapy, though tears that cause persistent locking or giving way may need a procedure to trim or repair the damaged cartilage. Pes anserine bursitis often responds to ice, stretching the hamstrings, and avoiding the specific movements that provoke it. Osteoarthritis is managed with a combination of activity modification, strengthening, and sometimes injections or bracing to offload the worn compartment.
Signs That Need Prompt Attention
Most inner knee pain can be evaluated at a routine appointment, but certain symptoms warrant urgent care. If your knee suddenly swelled after an injury, made a popping sound at the time of injury, can’t bear weight, looks bent or deformed, or is causing intense pain, get to an urgent care or emergency room. A fever combined with a hot, swollen knee raises concern for infection and needs immediate evaluation.