Inner knee pain, also called medial knee pain, most often comes from an injury or irritation to one of several structures packed into the inside of the knee joint: the medial collateral ligament (MCL), the medial meniscus, the pes anserine bursa, or the cartilage surfaces themselves. The cause depends heavily on how the pain started, where exactly you feel it, and whether it came on suddenly or built up over time.
What’s on the Inner Side of Your Knee
The inner knee is more structurally complex than most people realize. The MCL runs vertically along the inside of the joint, connecting your thighbone to your shinbone and preventing the knee from bending inward. Just behind it sits the posterior oblique ligament, which helps stabilize rotation. The medial meniscus, a C-shaped piece of cartilage, acts as a shock absorber between the bones. And just below the joint line, three tendons merge together at a spot called the pes anserinus, with a fluid-filled sac (bursa) cushioning them against the shinbone.
Any of these structures can become a source of pain, and the location of your discomfort, even by an inch or two, often points toward the cause.
MCL Sprains and Tears
The MCL is the most commonly injured ligament on the inner knee. It typically gets hurt when a force pushes the knee inward, like a hit to the outside of the leg during a sport, or when the knee twists awkwardly during a sudden change of direction. Injuries are graded by severity.
A grade 1 sprain means less than 10% of the ligament fibers are torn. You’ll feel tenderness and mild pain along the inner knee, but the joint stays stable. Most people can still walk, though it hurts. A grade 2 sprain is a partial tear, usually of the outer layer of the ligament. Pain and tenderness along the inner side are more intense, and the knee feels loose when moved by hand. Walking may be difficult because the joint isn’t as stable. A grade 3 tear means the ligament is completely ruptured, both its superficial and deep layers. The knee is very unstable, and weight-bearing is extremely painful. Complete MCL tears frequently occur alongside other injuries, particularly ACL tears.
Recovery timelines vary significantly by grade. Mild sprains often heal within a few weeks with rest and bracing. Moderate tears take longer and may require structured rehabilitation. Severe tears, especially those combined with ACL damage, can require months of recovery or surgical repair.
Medial Meniscus Tears
The meniscus on the inner side of the knee tears more often than the one on the outer side, partly because it’s less mobile and absorbs more load. In younger people, tears usually happen during a forceful twist or pivot, like cutting sharply during a run, or from deep squatting and heavy lifting. In older adults, the meniscus wears down over time, and a tear can happen with little or no obvious trauma.
The hallmark symptoms of a meniscus tear are distinct from ligament injuries. You may feel a popping sensation at the time of injury, followed by swelling and stiffness over the next day or two. Pain tends to spike when you twist or rotate the knee. The most telling sign is mechanical: your knee may lock in place so you can’t fully straighten it, or it may catch during movement. Some people describe a feeling of the knee giving way, as though it can’t be trusted to hold weight.
These mechanical symptoms, locking and catching in particular, help distinguish a meniscus tear from other causes of inner knee pain. If your knee simply aches but moves freely, something else is more likely.
Pes Anserine Bursitis
If your pain is located about 2 to 3 inches below the knee joint on the inner side of the shinbone, the problem is likely pes anserine bursitis. The bursa at this spot sits between the shinbone and three tendons that converge there, and it becomes inflamed from repetitive stress, particularly running, cycling, or activities involving a lot of stair climbing.
This condition feels different from ligament or meniscus injuries. The pain develops gradually rather than from a single event, worsens during physical activity or when climbing stairs, and improves with rest. It’s especially common in runners, people with tight hamstrings, and those who are overweight, since excess weight increases the load on this area. Pressing directly on the spot usually reproduces the pain clearly, which makes it relatively straightforward to identify.
Osteoarthritis of the Inner Knee
The inner (medial) compartment of the knee bears more weight than the outer side during normal walking, which is why osteoarthritis tends to develop there first. Cartilage gradually wears away, and the bones begin bearing more direct contact with each movement.
Osteoarthritis pain has a characteristic pattern. It hurts during or after movement, not typically at rest. Stiffness is worst first thing in the morning or after sitting for a while, then loosens up as you move. Over months and years, the pain becomes more persistent and the range of motion decreases. Unlike an acute injury, there’s no single moment when the pain starts. It creeps in. Increased body weight accelerates the process by adding stress to the joint with every step.
If you’re over 50 and your inner knee pain has been gradually worsening for months without a specific injury, osteoarthritis is one of the most likely explanations.
Plica Syndrome
A plica is a fold of tissue in the joint lining that most people have but never notice. When this fold becomes irritated from overuse or a direct blow, it thickens and catches during movement. Plica syndrome causes pain, swelling, and a clicking or popping sensation when bending or straightening the knee. It often worsens after squatting, climbing stairs, or sitting for long periods.
Plica syndrome can mimic a meniscus tear, but there’s a useful distinction. With a meniscus tear, pain and tenderness tend to sit right at the joint line, the seam where the thighbone meets the shinbone. With plica syndrome, the pain is typically above the joint line, and you may be able to feel the thickened tissue when pressing near the kneecap.
How to Narrow Down the Cause
The pattern of your pain carries a lot of diagnostic information. Consider these questions:
- Did it start suddenly or gradually? A sudden onset after a twist or impact points toward an MCL sprain or meniscus tear. A slow buildup suggests bursitis, osteoarthritis, or plica syndrome.
- Where exactly is the pain? Right along the joint line suggests the meniscus or MCL. Two to three inches below the joint suggests pes anserine bursitis. Above the joint line points toward plica syndrome.
- Does the knee lock or catch? Mechanical symptoms like locking, catching, or the knee giving way are characteristic of meniscus tears.
- Does it feel unstable? A sense that the knee could buckle inward, especially when changing direction, suggests MCL damage.
- Does rest help? Bursitis and plica syndrome usually improve with rest. Osteoarthritis pain often flares after rest and eases with gentle movement. Meniscus tears may hurt regardless.
When Inner Knee Pain Needs Urgent Attention
Most causes of inner knee pain respond to rest, ice, and time. But certain situations call for prompt evaluation. If you can’t move or put weight on your knee at all, don’t try to push through it. If the pain followed a severe fall, car accident, or direct blow and you suspect a broken bone, that warrants an emergency room visit. Pain that’s bad enough to disrupt your daily routine, makes it hard to move normally, or persists for more than a few days in a row is worth getting assessed even if the injury didn’t seem dramatic at the time.