Pain on the sides of your knees usually comes from soft tissue problems rather than the joint itself. The outer (lateral) side and inner (medial) side have different structures, so the location of your pain is the single most useful clue for narrowing down the cause. Most side-of-knee pain responds well to rest, targeted exercises, and correcting the movement patterns that triggered it.
Outer Knee Pain
Iliotibial Band Syndrome
The most common reason for pain on the outside of your knee is iliotibial band syndrome, or ITBS. Your iliotibial band is a thick strip of connective tissue that runs from the top of your pelvis all the way down the outside of your thigh to your knee. When it gets too tight, it rubs against the bony bump on the outer edge of your knee, causing irritation and swelling. The pain is typically aching or sharp and sits right on that outer knob of bone.
ITBS is especially common in runners, cyclists, and hikers. Several factors increase your risk: weak hip, glute, or core muscles; feet that roll inward or outward too much; ramping up your training too quickly; and skipping warm-ups or cool-downs. Some people are simply born with a tighter iliotibial band, which makes them more prone to flare-ups even at moderate activity levels.
Cyclists get a specific version of this problem. Riding with a saddle set too high forces the hamstrings and iliotibial band to overextend on every pedal stroke, concentrating stress on the outside of the knee. If your knees track outward during pedaling, often from foot positioning on the pedal, that compounds the issue.
Lateral Meniscus Tear
Your lateral meniscus is a crescent of cartilage that cushions the outer compartment of your knee joint. A tear here causes pain on the outside of the knee, often accompanied by a popping sensation at the time of injury. Afterward, you may notice swelling, stiffness, a feeling that your knee could give out, or a locking sensation where you can’t fully straighten or bend your leg. Lateral meniscus tears typically happen during twisting or pivoting motions, especially in sports like soccer, basketball, or tennis.
Lateral Collateral Ligament Injury
The ligament on the outer side of your knee can be sprained or torn by a direct blow to the inner knee that forces the joint to buckle outward. This is less common than inner ligament injuries but produces sharp pain on the outer edge of the knee, along with instability when walking or standing.
Inner Knee Pain
MCL Sprain or Tear
The medial collateral ligament connects your thighbone to your shinbone along the inner edge of the knee. It’s the most frequently injured knee ligament, usually damaged by a force that pushes the knee inward, like a tackle to the outside of the leg. You may hear a pop at the moment of injury, followed by pain and tenderness along the inner side of the knee.
MCL injuries are graded by severity. A grade 1 tear means fewer than 10% of the fibers are torn. Your knee still feels stable, and pain is mild. A grade 2 tear is a partial tear of the ligament, with more intense pain and noticeable looseness when the knee is moved. A grade 3 tear is a complete rupture. Recovery times reflect these grades: roughly 1 to 2 weeks for grade 1, 2 to 4 weeks for grade 2, and 4 to 8 weeks for grade 3.
Medial Meniscus Tear
The inner meniscus absorbs shock on the medial side of the knee and tears more often than the lateral one. Symptoms mirror those of a lateral tear (popping, swelling, locking, giving way) but the pain and tenderness sit along the inner joint line. Medial meniscus tears are common in both athletes and older adults whose cartilage has worn down over time.
Pes Anserine Bursitis
If your pain is on the inner side of your knee but slightly below the joint, about 2 to 3 inches down your shinbone, a small fluid-filled sac called the pes anserine bursa may be inflamed. This bursa sits between your shinbone and three tendons that converge there. Pes anserine bursitis is most common in athletes, women between 40 and 60, and people with diabetes, osteoarthritis, or excess body weight. It often develops from repetitive bending motions or suddenly increasing activity.
Causes That Affect Either Side
Osteoarthritis
Wear-and-tear arthritis can produce pain on one or both sides of the knee depending on which compartment is breaking down. The inner (medial) compartment is affected far more often. A large meta-analysis found that isolated medial compartment arthritis accounted for about 27% of all knee osteoarthritis cases, while isolated lateral compartment involvement made up only about 5%. If you’re over 50 and your side-of-knee pain is a gradual, worsening ache that’s worse after activity or in the morning, osteoarthritis is a likely contributor.
Kneecap Tracking Problems
Your kneecap is supposed to glide straight up and down in a groove on your thighbone. When the muscles and connective tissue around it pull unevenly, the kneecap drifts to one side, a condition called patellofemoral pain syndrome. The inner thigh muscle that pulls the kneecap inward is often too weak relative to the outer structures (the iliotibial band and outer thigh muscle), so the kneecap tends to track laterally. This creates pain that can wrap around the sides of the knee, particularly during squatting, stair climbing, or sitting for long periods.
Plica Syndrome
A plica is a fold of tissue lining the inside of your knee joint. When this fold becomes irritated from overuse or a direct hit, it thickens and catches during movement, producing pain and swelling in the middle to inner part of the knee. Plica syndrome is often confused with a meniscus tear, but the pain tends to sit above the joint line rather than right along it.
How to Tell Which Problem You Have
Start with location. Pinpoint where the pain is strongest using your finger. Outer knee pain that worsens with running or cycling and eases with rest points toward ITBS. Inner knee pain after a specific twisting or impact event suggests an MCL sprain or meniscus tear. A gradual onset of inner knee pain lower than the joint line, especially if you’re a runner or have arthritis, fits pes anserine bursitis.
Next, consider how the pain behaves. Pain that builds during activity and disappears with rest is more typical of overuse conditions like ITBS, bursitis, or patellofemoral syndrome. Pain that appeared suddenly with a pop, especially alongside swelling or a feeling of instability, suggests a ligament or meniscus injury. Locking or catching sensations point toward a meniscus tear or plica syndrome.
Strengthening That Helps Most Side Knee Pain
Weak hip and glute muscles are a recurring theme across nearly every cause of side-of-knee pain. Your gluteus medius, the muscle on the outer surface of your hip, stabilizes your pelvis and controls how your thighbone angles into the knee. When it’s underactive, your knee absorbs forces it wasn’t designed to handle alone.
Several exercises specifically target this muscle and are widely recommended by physical therapists:
- Side-lying hip abduction: Lie on your side with your bottom leg bent and top leg straight. Lift the top leg toward the ceiling, squeeze at the top, and lower slowly.
- Clamshells: Same side-lying position but with both legs bent. Keep your feet together and rotate your top knee open like a clamshell, driving the motion from your hip.
- Lateral band walks: Place a resistance loop around your ankles or just above your knees, sit into a quarter squat, and step sideways while keeping tension on the band throughout.
- Monster walks: Same band setup and quarter-squat position, but step diagonally forward instead of sideways, then walk backward to the start.
- Single-leg wall lean: Stand next to a wall, lift the leg closest to the wall to 90 degrees, and press that knee into the wall. The standing leg’s hip muscles fire hard to keep your pelvis level.
For overuse conditions like ITBS and pes anserine bursitis, foam rolling the tight structures alongside this strengthening work helps restore balance. For ligament injuries, a structured rehab program that progresses from range-of-motion work to strength training to sport-specific movements is the standard path back. Meniscus tears that lock the knee or don’t improve with conservative treatment sometimes require a procedure to trim or repair the torn cartilage.