Pain on the inside of your knee, known as the medial side, is one of the most common knee complaints. It can come from a ligament sprain, a torn piece of cartilage, inflamed tendons, or simply wear and tear on the joint. The cause often depends on how the pain started, what makes it worse, and exactly where you feel it. 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 the most common ligament injured in the knee, and it usually happens when the knee is forced sideways, such as a direct hit to the outside of the leg, a sudden pivot, or an awkward landing. You’ll typically feel sharp pain right along the inner joint line, and the area will be tender to touch.
MCL injuries are graded by severity. A grade 1 sprain means less than 10% of the ligament fibers are torn. Your knee still feels stable, and you’ll have mild tenderness and pain. A grade 2 sprain is a partial tear, where the knee feels loose when moved by hand and the pain along the inner side is intense. A grade 3 tear is a complete rupture, with significant instability and severe pain.
The good news is that MCL sprains generally heal well without surgery because the ligament has a strong blood supply. A mild grade 1 sprain often allows return to full activity within one to two weeks. Grade 2 injuries take longer, typically several weeks in a brace with gradual rehabilitation. Grade 3 tears may take two to three months, though surgery is rarely needed unless other structures in the knee are also damaged.
Medial Meniscus Tear
Each knee has two C-shaped pieces of cartilage called menisci that sit between the thighbone and shinbone, acting as shock absorbers. The medial meniscus, on the inner side, tears far more often than the one on the outer side. In one MRI study of 100 symptomatic knees, 50 had medial meniscus tears compared to only 16 with lateral tears.
A meniscus tear feels different from a ligament injury. The hallmark symptoms are mechanical: your knee catches, locks, or clicks during movement. Pain accompanied by a snapping or popping sound, especially in the back of the knee, suggests a tear in the rear portion of the medial meniscus. You might find that your knee locks in a bent position and won’t fully straighten, or that it gives way unexpectedly. Swelling usually develops gradually over a day or two rather than appearing instantly.
Meniscus tears can happen from a sudden twist during sports, but they also occur from everyday movements as the cartilage weakens with age. Small tears often improve with rest, ice, and physical therapy. Larger tears that cause persistent locking or catching are more likely to need surgical repair.
Pes Anserine Bursitis
If your pain is located slightly below the inner joint line, roughly two to three inches below the knee cap on the inner side of your shinbone, the cause may be pes anserine bursitis. This is inflammation of a small fluid-filled sac (bursa) that sits between the shinbone and three tendons that attach there.
This condition is especially common in runners and in people who already have osteoarthritis. The pain tends to worsen with stairs, and the area is noticeably tender when you press on it. Unlike a meniscus tear, there’s no clicking or locking involved. It’s primarily a pain-and-tenderness problem that responds well to rest, icing, and stretching the hamstrings and inner thigh muscles.
Plica Syndrome
A plica is a fold of tissue in the lining of your knee joint. Most people have them without any problems, but when a plica along the inner side of the knee becomes irritated, usually from repetitive bending, it can swell and cause pain in the middle of the knee. You may also notice clicking, popping, or a reduced range of motion.
Plica syndrome is easy to confuse with a meniscus tear because both cause inner knee pain and clicking. One useful distinction: meniscus pain and tenderness are typically right at the joint line, while plica syndrome pain tends to sit above the joint line, closer to the kneecap. The condition usually improves with rest and anti-inflammatory measures, though persistent cases sometimes require a minor procedure to remove the irritated tissue.
Osteoarthritis
In people over 50, or younger adults with a history of knee injuries, gradual-onset inner knee pain is often caused by osteoarthritis. The medial compartment of the knee bears the most weight during walking, so it’s the area where cartilage wears down first. The pain typically feels stiff and achy, worse in the morning or after sitting for a long time, and improves somewhat with gentle movement. Over time, you may notice the knee feels crunchy or grinds when you bend it.
Unlike a sudden injury, osteoarthritis develops slowly. The knee may ache more on some days than others, and flare-ups often follow periods of increased activity. Weight management, low-impact exercise, and targeted strengthening are the foundation of long-term management.
How to Tell These Causes Apart
The onset and character of your pain are the best clues. A sudden injury with a pop suggests a ligament tear or meniscus damage. Catching, locking, or clicking points toward a meniscus tear. Pain that developed gradually and sits a few inches below the joint favors bursitis. Stiffness that’s worse after rest and improves with movement leans toward arthritis.
When you see a provider, they’ll likely perform a few hands-on tests. For a suspected MCL injury, they’ll gently push the knee inward while it’s slightly bent, checking for looseness and pain. For a meniscus tear, they’ll bend the knee to 90 degrees, rotate the lower leg inward and outward, then straighten it, feeling for clicks or pain. These physical tests aren’t perfect on their own, so imaging, particularly an MRI, is often used to confirm the diagnosis.
Strengthening and Recovery
Regardless of the specific cause, the approach to most inner knee pain involves reducing inflammation first, then rebuilding the strength and flexibility of the muscles that support the joint. Strong quadriceps, hamstrings, and hip muscles absorb more shock, reducing the load on the inner knee structures.
A conditioning program recommended by the American Academy of Orthopaedic Surgeons targets five muscle groups: the quadriceps (front of the thigh), hamstrings (back of the thigh), outer thigh muscles, inner thigh muscles, and glutes. The program calls for two to three sessions per week over four to six weeks, starting each session with five to ten minutes of low-impact warmup like walking or stationary cycling, followed by stretching, then strengthening exercises, and finishing with another round of stretching.
The key rule during rehab is that you should not feel pain during an exercise. Discomfort from effort is normal, but sharp or worsening pain in the knee means you need to stop or modify the movement. Once you’ve recovered, continuing these exercises as a maintenance routine helps protect the knee long-term.
Signs You Need Urgent Care
Most inner knee pain can wait for a scheduled appointment, but certain signs call for immediate attention. According to Mayo Clinic, you should seek urgent care if your knee joint looks bent or deformed, you heard a popping sound at the time of injury, the knee can’t bear weight at all, you have intense pain, or the knee swelled up suddenly. These signs can indicate a severe ligament tear, fracture, or other structural damage that needs rapid evaluation.