Inner knee pain, also called medial knee pain, most often comes from one of a handful of causes: a ligament sprain, a meniscus tear, bursitis, or early arthritis. Which one is behind your pain depends on how it started, where exactly it hurts, and what makes it worse. Here’s how to narrow it down.
MCL Sprain or Tear
The medial collateral ligament (MCL) runs along the inner edge of your knee, connecting your thighbone to your shinbone. It’s one of the most commonly injured knee ligaments, and it usually happens when a force pushes the knee inward, like a hit from the side during sports or an awkward landing. The hallmark sign is tenderness right along the inner joint line, and depending on severity, your knee may feel loose or unstable.
MCL injuries are graded by how much of the ligament is torn. A grade 1 tear means less than 10% of the fibers are damaged. You’ll feel tenderness and mild pain, but the knee stays stable. These heal in one to three weeks. A grade 2 tear is a partial tear, usually of the outer layer of the ligament. Pain is more intense, and the knee feels loose when someone moves it by hand. Recovery takes four to six weeks. A grade 3 tear is a complete rupture of both layers. The knee is very unstable, the pain is severe, and healing takes six weeks or longer. Most MCL tears, even complete ones, heal without surgery if properly braced and rehabilitated.
Medial Meniscus Tear
Each knee has two C-shaped pads of cartilage called menisci that act as shock absorbers between your thighbone and shinbone. The medial meniscus sits on the inner side, and it tears more often than the outer one. In younger people, this usually happens during a twisting motion with the foot planted. In people over 40, the cartilage can wear down and tear with minimal force, sometimes just from squatting or stepping off a curb.
The classic symptoms are pain on the inner side of the knee, swelling that builds over hours rather than appearing instantly, and mechanical symptoms like clicking, catching, or locking when you bend the knee. Squatting tends to make it worse. Joint line tenderness, meaning pain when you press right along the seam of the knee joint, is the most reliable physical sign.
For degenerative tears in middle-aged and older adults, physical therapy works as well as surgery. A study of more than 270,000 people aged 45 to 70 found that knee function and long-term risk of developing osteoarthritis were similar whether people had arthroscopic surgery or completed eight weeks of physical therapy (16 half-hour sessions). Surgery may still make sense for younger patients with acute tears that cause persistent locking, but physical therapy is a strong first option for most people.
Pes Anserine Bursitis
If your pain is located about two to three inches below the inner joint line, closer to the top of your shinbone, the culprit may be pes anserine bursitis. A bursa is a small fluid-filled sac that reduces friction between tendons and bone. The pes anserine bursa sits where three hamstring tendons attach to the inner shin, and when it gets inflamed, it produces a localized aching pain that’s often worse with stairs or getting up from a chair.
This condition is common in runners, people with osteoarthritis, and people carrying extra weight. Specific risk factors include tight hamstrings, sudden increases in running mileage, excessive hill training, and structural alignment issues like knock knees. It responds well to rest, ice, and stretching the hamstrings. Most cases resolve in a few weeks once the irritating activity is modified.
Medial Plica Syndrome
A plica is a fold of tissue inside the knee joint left over from development. Most people have them and never notice. But in some cases, particularly in runners and athletes who do a lot of repetitive bending, the plica on the inner side of the knee thickens and becomes irritated. It can rub across the end of the thighbone or the underside of the kneecap, causing a dull ache and sometimes a snapping or popping sensation with movement.
Plica syndrome often mimics a meniscus tear because both cause inner knee pain with occasional popping. The key difference is that plica pain tends to be slightly higher, closer to the kneecap, and you can sometimes feel a tender band of tissue when you press the area. It usually improves with activity modification, stretching, and strengthening exercises.
Osteoarthritis of the Inner Knee
The inner (medial) compartment of the knee bears more weight than the outer side, which is why it wears out first. About 27% of all knee osteoarthritis cases affect the medial compartment alone, making it the single most common pattern of knee arthritis. Pain tends to develop gradually over months or years, feels stiff in the morning or after sitting, and worsens with prolonged walking or standing. There’s no single injury to point to; it’s cumulative wear.
Risk increases with age, previous knee injuries, excess body weight, and jobs or sports that put repetitive stress on the joint. Early arthritis often responds well to strengthening the muscles around the knee, maintaining a healthy weight, and staying moderately active. The goal is to slow progression and manage symptoms rather than reverse the damage.
How to Tell Which Cause Fits
The circumstances around your pain offer the strongest clues. A sudden onset during a sport or awkward twist points toward an MCL sprain or meniscus tear. Pain that builds gradually without a clear injury suggests arthritis, bursitis, or plica syndrome. Where you feel it matters too: pain right at the joint line suggests a meniscus or MCL issue, pain a few inches below the joint suggests bursitis, and pain closer to the kneecap leans toward plica syndrome or early arthritis.
Mechanical symptoms like catching, locking, or a sensation that something is stuck inside the joint strongly suggest a meniscus tear. Instability, where the knee feels like it might buckle inward, points to an MCL injury. A dull, achy pain that comes and goes with activity levels is more typical of bursitis or arthritis.
Strengthening the Inner Knee
Regardless of the cause, strengthening the muscles that support the inner knee helps with both recovery and prevention. The key muscle groups are the quadriceps (especially the inner portion near the kneecap), the inner thigh muscles (adductors), and the hamstrings.
Hip adduction exercises, where you squeeze your legs together against resistance, target the inner thigh and help stabilize the medial side of the knee. You can start without weight and gradually add ankle weights, beginning around 5 pounds and working up to 10. Straight-leg raises, wall sits, and gentle hamstring stretches round out a basic program. The American Academy of Orthopaedic Surgeons recommends continuing a knee conditioning program for four to six weeks, two to three days per week, then maintaining it long-term.
Signs That Need Prompt Attention
Some inner knee symptoms warrant urgent evaluation. If your knee buckled and you heard a popping sound at the time of injury, if the joint is visibly deformed or bent at an unusual angle, if you can’t put any weight on it, or if it swelled rapidly within minutes, you should get to an urgent care or emergency room. These patterns suggest a significant structural injury.
Outside of an acute injury, schedule an appointment if your knee is badly swollen, red, warm to the touch, or increasingly painful over days. A hot, swollen joint combined with fever can signal an infection, which requires prompt treatment.