Pain on the left side of your right knee is pain on the inner, or medial, side of the joint. This is one of the most common locations for knee pain, and it can stem from several different structures packed into that area: the medial collateral ligament (MCL), the medial meniscus, a fluid-filled cushion called a bursa, or the joint surface itself. What’s causing yours depends on how the pain started, exactly where you feel it, and what makes it worse.
What’s on the Inner Side of Your Knee
The medial side of the knee contains a few key structures that are each vulnerable in different ways. The MCL is a band of tissue that connects your thighbone to your shinbone and prevents your knee from bending inward. The medial meniscus is a wedge of tough cartilage that cushions the gap between those two bones. Beneath the joint line, a small fluid-filled sac called the pes anserine bursa sits where three tendons from your thigh muscles attach to the top of your shinbone. And the joint surfaces themselves are lined with cartilage that can wear down over time.
Each of these structures produces pain in a slightly different spot and in response to different activities, which is useful for narrowing down the cause.
MCL Sprain or Tear
An MCL injury is one of the most common reasons for sudden medial knee pain, especially if you play sports. It happens when force pushes the knee inward, stretching or tearing the ligament. A direct hit to the outside of the knee, a sudden change of direction, or an awkward landing can all do it.
Typical signs include tenderness right along the inner edge of the knee, swelling, stiffness, and a feeling that the knee might give out under your weight. Some people hear or feel a pop at the moment of injury. If the ligament is significantly torn, the knee may feel loose or unstable when you try to push off or pivot.
Recovery time depends on severity. A mild (grade 1) sprain, where the ligament is stretched but intact, typically heals in one to three weeks. A moderate (grade 2) tear takes four to six weeks. A severe (grade 3) tear, where the ligament is fully ruptured, requires six weeks or more and sometimes a hinged brace to keep the knee stable while it heals. Most MCL injuries recover without surgery.
Medial Meniscus Tear
The medial meniscus is the cartilage pad on the inner side of your knee, and it tears when you twist your leg suddenly, often while your foot is planted. It can also wear down gradually with age, making it easier to tear from something as minor as a deep squat.
Meniscus tears produce a distinct set of symptoms. Pain tends to be right along the joint line, especially when you twist or rotate the knee. Swelling usually develops over several hours rather than instantly. The hallmark symptom is a mechanical problem: your knee may lock in place, catch during movement, or feel like it’s giving way. You might have trouble fully straightening the leg.
Small tears sometimes settle down with rest and physical therapy over several weeks. Larger tears, or those that cause persistent locking, may need a procedure to trim or repair the damaged cartilage.
Pes Anserine Bursitis
If the pain is below the joint line, about two to three inches down from the inner side of your knee, it’s more likely bursitis than a ligament or cartilage problem. The pes anserine bursa sits where three tendons from your inner thigh and hamstring muscles attach to the shinbone. When this bursa gets inflamed, you feel a specific, localized ache in that lower spot.
This condition is especially common in runners, cyclists, and people who do a lot of hill walking. It also affects people with osteoarthritis or those carrying extra body weight. The pain tends to worsen with stairs and prolonged walking, and the area is often tender to touch. Unlike ligament injuries, there’s usually no instability or locking.
Osteoarthritis
If your medial knee pain came on gradually over months or years rather than from a specific injury, osteoarthritis is a leading possibility. The inner compartment of the knee bears a significant share of your body weight, so it’s often the first area where cartilage wears thin. This leads to a deep, aching pain that’s worse after activity, especially walking, climbing stairs, or standing for long periods. Morning stiffness that eases after 20 to 30 minutes of movement is a classic pattern.
Osteoarthritis is more common after age 50, but previous injuries to the knee (even ones that healed well) raise the risk of developing it earlier. This is sometimes called post-traumatic arthritis.
Plica Syndrome
A less well-known cause of inner knee pain is plica syndrome. A plica is a fold of the tissue lining your knee joint, and the medial plica sits right along the inner edge. Normally it’s thin and flexible, but repeated bending, squatting, or stair climbing can irritate it, causing it to thicken and catch against the bone.
Plica syndrome produces pain and swelling on the inner side of the knee, along with clicking or popping when you bend or straighten the joint. It tends to flare up after activities involving repetitive knee bending, and many people notice a catching sensation when standing after sitting for a long time. You may even be able to feel the swollen fold when pressing around the kneecap. It’s often mistaken for a meniscus tear because the symptoms overlap, but imaging and a careful exam can distinguish the two.
Repetitive Strain and Overuse
Not all medial knee pain traces back to a single structure. Repetitive strain injuries happen when you load the knee with the same movement pattern too often, especially without adequate recovery. This is common in runners who suddenly increase mileage, cyclists with poor bike fit, or workers who spend long hours kneeling or squatting. The pain tends to build gradually, feel diffuse along the inner knee, and improve with rest only to return when you resume the activity.
How to Tell These Apart
A few practical clues can help you narrow down the cause before you see a provider:
- Location: Pain right along the joint line suggests a meniscus tear or arthritis. Pain along the inner edge of the knee, slightly above or at the joint, points toward the MCL. Pain two to three inches below the joint suggests pes anserine bursitis.
- Onset: Sudden pain after a twist, blow, or awkward step is more likely a ligament or meniscus injury. Gradual onset suggests arthritis, bursitis, or overuse.
- Mechanical symptoms: Locking, catching, or an inability to fully straighten the knee strongly suggests a meniscus tear. Instability or a sense the knee will buckle points toward an MCL tear.
- Aggravating activities: Pain that worsens with stairs, squatting, and prolonged sitting is common with plica syndrome and bursitis. Pain with twisting or pivoting is more typical of meniscus or ligament injuries.
Managing Medial Knee Pain
For most causes of inner knee pain, the initial approach is the same: reduce the load on the knee and control inflammation. Rest from the aggravating activity, apply ice for 15 to 20 minutes several times a day, and use compression if swelling is present. Over-the-counter anti-inflammatory medication can help in the short term.
Once the acute pain settles, strengthening the muscles around the knee is the most important step for long-term recovery. Strong quadriceps and hip muscles absorb shock that would otherwise go through the joint, reducing stress on the MCL, meniscus, and cartilage. A conditioning program targeting the inner thigh (adductor) muscles and the muscles along the front and back of the thigh is a good starting point. The American Academy of Orthopaedic Surgeons recommends continuing a knee strengthening program for four to six weeks, then maintaining it two to three times per week as ongoing protection.
For inner thigh strengthening, you can start with side-lying leg lifts using just your body weight, then progress to a 5-pound ankle weight and gradually work up to 10 pounds as the exercise gets easier.
Signs That Need Prompt Evaluation
Some patterns of medial knee pain warrant getting seen sooner rather than later. If your knee locks and you physically cannot straighten it, that suggests a meniscus fragment is caught in the joint. If the knee feels unstable or buckles when you walk, you may have a significant ligament tear. Rapid swelling within the first hour after an injury often means bleeding inside the joint. And if you cannot bear weight at all, imaging is important to rule out a fracture or severe soft tissue damage.