Inner knee pain, also called medial knee pain, usually comes from one of a handful of structures packed into a small area: a ligament, a piece of cartilage, a fluid-filled sac, or the joint surface itself. The cause depends on your age, activity level, and how the pain started. Some causes heal on their own in a few weeks, while others need targeted treatment. Here’s how to narrow it down.
What’s on the Inside of Your Knee
The inner side of your knee contains several structures that can each produce pain. The medial collateral ligament (MCL) runs along the inside of the joint and keeps your knee from bending inward. Beneath it sits the medial meniscus, a C-shaped piece of cartilage that cushions the space between your thighbone and shinbone. A small fluid-filled sac called the pes anserine bursa sits a few centimeters below the joint line, where three tendons from your hamstring and inner thigh muscles attach to the shinbone. And the joint surface itself, lined with smooth cartilage, can wear down over time.
Because these structures overlap in such a tight space, inner knee pain can feel similar regardless of the source. The specifics of when and how it hurts are what point toward one cause over another.
MCL Sprain or Tear
The MCL is the most commonly injured ligament in the knee, and it typically gets hurt when a force pushes the knee inward, like a hit to the outside of the leg during sports, or an awkward landing. You’ll feel sharp pain directly along the inner edge of the joint, and the area will be tender to touch.
MCL injuries are graded by severity. A grade 1 tear means less than 10% of the ligament fibers are damaged. Your knee still feels stable, and you’ll have tenderness with mild pain. This usually heals within one to three weeks. A grade 2 tear is a partial tear of the ligament. The knee feels loose when moved, and pain along the inner side is intense. Recovery takes four to six weeks. A grade 3 tear is a complete rupture. The knee is very unstable, and pain is severe. Healing takes six weeks or longer.
Most MCL injuries heal without surgery because the ligament has a good blood supply. Treatment centers on protecting the knee with a brace, controlling swelling, and gradually rebuilding strength.
Medial Meniscus Tear
The medial meniscus tears more often than the lateral one, partly because it’s less mobile and absorbs more force during twisting movements. A tear can happen suddenly during a sport (a deep squat, a pivot, a sudden stop) or gradually as the cartilage wears down with age.
The hallmark symptoms are pain along the inner joint line that worsens with twisting or rotating, swelling or stiffness, a popping sensation at the time of injury, and difficulty fully straightening the knee. Some people describe a locking sensation, where the knee gets stuck and won’t move, or a feeling that the knee is about to give way. These mechanical symptoms suggest a flap of torn cartilage is catching inside the joint.
For degenerative meniscus tears, which are common in people over 40, physical therapy is the recommended first-line treatment for three to six months. A 2024 consensus statement from European and American orthopedic societies confirmed that outcomes from physical therapy and surgery are comparable for these tears. A ten-year follow-up study found that exercise therapy and surgical removal of the torn portion produced equal long-term results. About 30% of people who start with conservative treatment eventually opt for surgery due to persistent symptoms, but the majority do well without it. Traumatic tears in younger, active people, especially those with locking, are more likely to benefit from surgical repair.
Pes Anserine Bursitis
If your pain is below the joint line rather than right at it, the pes anserine bursa is a likely culprit. This small sac sits about 5 to 7 centimeters below the inner edge of the knee, where three tendons converge on the shinbone. When it becomes inflamed, you feel a localized ache on the upper inner shin that worsens with stairs, getting up from a chair, or walking.
Tight hamstrings are a major driver. They increase friction over the bursa with every step. Other risk factors include obesity, flat feet (which shift pressure toward the inner knee), knock-kneed alignment, osteoarthritis, and sports that involve a lot of lateral movement like basketball or tennis. It’s especially common in middle-aged women.
This condition responds well to rest, ice, hamstring stretching, and sometimes a corticosteroid injection. If flat feet are contributing, supportive insoles can help by correcting the alignment of your lower leg.
Medial Compartment Osteoarthritis
The inner side of the knee is the most common location for osteoarthritis to develop, particularly in people who are slightly bowlegged. Over time, the cartilage on the inner surfaces of the thighbone and shinbone wears thin, eventually leading to bone grinding against bone.
Early on, you’ll notice a dull ache on the inner side that worsens with activity and improves with rest. Morning stiffness that eases after 20 to 30 minutes of movement is typical. As the condition progresses, the knee may swell after longer walks, feel stiff climbing stairs, and hurt even at rest. Many people develop increased bowlegged alignment as cartilage loss narrows the inner joint space.
Initial treatment focuses on weight management, low-impact exercise, and strengthening the muscles around the knee. For advanced cases where bone is grinding on bone in the inner compartment while the rest of the knee remains healthy, surgical options include realignment procedures that shift load away from the damaged side, or partial knee replacement that resurfaces only the worn compartment.
Plica Syndrome
A less well-known cause of inner knee pain involves the medial plica, a fold of tissue left over from fetal development that lines the inner wall of the knee joint. Most people have one and never notice it. But if it becomes thickened or inflamed from repetitive bending, it can snap over the inner edge of the thighbone and cause clicking, catching, and a dull ache.
Plica syndrome mimics a meniscus tear closely enough that it’s often misdiagnosed. One distinguishing feature: meniscus pain tends to be right at the joint line, while plica pain is typically felt just above it. The catching sensation is more noticeable after sitting for a long time and then standing up. Symptoms often worsen with squatting, stair climbing, and prolonged sitting.
Most cases resolve with rest, anti-inflammatory measures, and physical therapy. If the plica remains problematic, it can be removed arthroscopically.
Exercises That Support the Inner Knee
Regardless of the underlying cause, strengthening the muscles on the inner side of your thigh helps stabilize the knee and reduce pain. The key muscle is the vastus medialis oblique (VMO), the teardrop-shaped muscle just above and to the inside of your kneecap. When it’s weak, the kneecap tracks poorly and the inner knee bears uneven loads.
Closed-chain knee extensions, where your foot stays in contact with a surface while you straighten your leg, produce the highest VMO activation. A practical version: lie on your back with your heels elevated on a chair or stability ball, lift your hips, then slowly straighten your legs and hold for five seconds. Straight-leg raises while lying on your side, lifting the bottom leg toward the top one, also activate the VMO through a hip adduction movement. Standard mini-squats to about 60 degrees of knee bend, with a ball squeezed between your knees, combine quad strengthening with inner-thigh engagement.
Start with sets you can do without pain. If an exercise increases your knee pain, back off the range of motion or reduce the load rather than pushing through it.
Signs That Need Urgent Attention
Most inner knee pain can be managed with some initial rest and a gradual return to activity. But certain signs warrant an urgent visit. Get to an emergency room or urgent care if your knee joint looks visibly deformed or bent at an odd angle, you heard a pop at the time of injury and the knee swelled rapidly, you can’t put any weight on the leg, or you have sudden intense swelling without an obvious injury (which can signal infection or other serious problems). A knee that locks completely and won’t unlock also needs prompt evaluation, as a displaced meniscus fragment may need to be addressed surgically.