Right knee pain has dozens of possible causes, and the single most useful clue is where exactly it hurts. Pain in the front, sides, or back of the knee each point to a different set of structures, and the activities that make it worse narrow things down further. Knee pain affects roughly 25% of adults, so you’re far from alone in searching for answers.
Pain in the Front of the Knee
The most common cause of pain around or behind the kneecap is patellofemoral pain syndrome, sometimes called runner’s knee. It flares during weight-bearing activities that bend the knee: running, climbing stairs, jumping, squatting, or sitting for long periods with your knees bent. If squatting reliably reproduces your pain, that’s the single most telling sign.
Patellar tendonitis (jumper’s knee) produces pain just below the kneecap, where the tendon connecting the kneecap to the shinbone becomes inflamed and swollen. It’s especially common in people who do repetitive jumping or sprinting. The tenderness is very localized to the tendon itself, which helps distinguish it from the broader, less precise ache of patellofemoral pain syndrome.
A few less common front-of-knee causes are worth knowing about. Osgood-Schlatter disease causes tenderness and swelling right where the patellar tendon attaches to the bump below your kneecap, and it’s most common in adolescents during growth spurts. Patellar instability gives a sensation that the kneecap is slipping or shifting, with intermittent pain rather than constant soreness. And Hoffa disease involves the fat pad just below the kneecap, producing pain and tenderness in that specific spot.
Pain on the Inner Side
Inner (medial) knee pain usually comes down to two structures: the medial collateral ligament (MCL) or the medial meniscus. Both can be injured during a twist, a direct blow, or even gradual wear over time, but they feel different in practice.
An MCL injury causes tenderness running along the inner edge of the knee. You might feel a sense of looseness or instability, as though the knee could give way sideways. Weight-bearing is uncomfortable but often still possible. A meniscus tear, on the other hand, tends to produce pain along the joint line itself, sometimes with a popping sensation at the time of injury. The hallmark signs are catching, locking, or difficulty fully straightening the leg. Weight-bearing is commonly painful.
Degenerative meniscus tears become increasingly common with age. Among people 65 to 70, about 32% have a medial meniscus tear visible on imaging. That number climbs to roughly 48% by ages 75 to 80 and exceeds 52% after 80. Many of these tears cause no symptoms at all, which is why imaging alone doesn’t always explain the pain.
Pain on the Outer Side
The most frequent cause of outer (lateral) knee pain is iliotibial band syndrome. The iliotibial band is a thick strip of connective tissue that runs from your pelvis down the outside of your thigh to just below the knee. When it’s tight, it rubs against the bony bump on the outer edge of your thighbone every time you bend and straighten your knee. That repeated friction causes irritation and a sharp or burning pain on the outside of the knee.
IT band syndrome is especially common in runners, cyclists, and hikers. The pain typically starts after a predictable distance or duration of activity and worsens if you push through it. It often eases with rest but returns as soon as you resume the aggravating activity. Other possible causes of outer knee pain include lateral meniscus tears and lateral collateral ligament injuries, which is why imaging is sometimes needed to sort things out.
Pain Behind the Knee
A Baker cyst (also called a popliteal cyst) is a fluid-filled swelling that forms in the hollow behind the knee. It creates a visible bulge, a feeling of tightness, and stiffness that makes it hard to fully bend the knee. Pain worsens with activity or when you try to fully straighten or bend the joint.
Baker cysts are rarely a problem on their own. They’re almost always caused by an underlying issue inside the knee, such as osteoarthritis or a cartilage tear. These conditions cause the joint to produce excess lubricating fluid, which then pushes backward into a small sac behind the knee. Treating the underlying cause is what ultimately resolves the cyst.
Hamstring tendon irritation can also produce pain behind the knee, particularly during activities that involve bending the knee against resistance, like sprinting or deep lunging.
Bursitis vs. Tendonitis
These two conditions overlap in symptoms but involve different structures. Tendonitis is inflammation or irritation of a tendon, the cord that connects muscle to bone. Bursitis involves the bursae, which are small fluid-filled cushions that reduce friction between bones, muscles, and tendons. In the knee, bursitis often produces visible, localized swelling that feels spongy, while tendonitis causes pain that worsens with specific movements but doesn’t always produce obvious swelling. Both can occur at the same time, and both respond well to activity modification and gradual strengthening.
Signs That Need Urgent Attention
Most knee pain improves with time and sensible management, but certain symptoms call for prompt evaluation:
- Visible deformity or an obviously misaligned joint
- A popping sound at the time of injury followed by rapid swelling
- Inability to bear weight on the leg
- Sudden, significant swelling that develops within hours
- Intense pain that doesn’t ease with rest
A knee that is red, warm, tender, and swollen, especially with a fever, could signal infection or an inflammatory condition and warrants medical evaluation even if it didn’t follow an obvious injury.
Managing Knee Pain at Home
For a fresh injury, sports medicine guidelines now recommend an approach called PEACE and LOVE, which has replaced the older RICE method. In the first one to three days, the priority is protecting the knee by reducing movement enough to prevent further damage, but not resting so long that the tissue weakens. Elevate the leg above heart level when possible, and use compression with a bandage or sleeve to control swelling.
One counterintuitive point: avoiding anti-inflammatory medications in the early days may actually help. Inflammation is part of the repair process, and suppressing it with medication, especially at higher doses, can interfere with long-term tissue healing.
After those first few days, the focus shifts to gradual loading. Start moving and adding gentle stress to the knee as soon as pain allows. Pain-free aerobic exercise, even something as simple as walking or cycling, increases blood flow to the injured area and supports recovery. The goal is to progressively build the tissue’s tolerance rather than waiting for pain to disappear completely before moving.
Strengthening for Long-Term Relief
For patellofemoral pain and many other common knee complaints, strengthening the quadriceps is the most effective long-term strategy. You may have heard that targeting the inner portion of the quadriceps (the VMO) is the key to better kneecap tracking. Older rehab programs were built around this idea. But research has consistently shown that you can’t selectively strengthen the VMO in isolation. In one study comparing a standard leg press to a leg press combined with hip squeezing (designed to target the VMO), the standard leg press actually produced better results.
What does work is a general quadriceps strengthening program. Exercises like squats, step-downs, leg presses, and lunges build overall thigh strength, which supports and stabilizes the kneecap. Hip strengthening matters too, particularly the muscles that control rotation and sideways movement. Weakness in the hips changes how forces travel through the knee, and strengthening them often resolves knee pain that seemed to resist other treatment.
Consistency matters more than exercise selection. Most people notice meaningful improvement within six to eight weeks of regular strengthening, though some causes of knee pain take longer to fully resolve.