Damaged knee cartilage typically produces a deep, vague ache inside the joint, often accompanied by mechanical sensations like catching, locking, or grinding when you bend or straighten your leg. Unlike a sharp muscle pull or a bruise you can point to, cartilage pain is harder to pin down. It can feel like something is “off” inside the knee without a clear source, and it tends to worsen with specific movements rather than hurting constantly.
The Pain Itself
Cartilage has no nerve endings, so the pain you feel doesn’t come directly from the damaged tissue. Instead, it comes from the surrounding structures reacting to the damage: inflamed joint lining, exposed bone surfaces, or loose fragments irritating the joint. This is why cartilage pain often feels diffuse and hard to locate. You might describe it as a dull ache deep inside the knee rather than a pinpoint sting.
The pain usually localizes to the side of the knee where the damage has occurred, but it can also settle behind the kneecap or spread throughout the entire joint. If the damage involves the cartilage on the underside of the kneecap or the groove it slides through, the pain tends to concentrate around or behind the kneecap and flares during activities that load the bent knee.
Stiffness often accompanies the pain, especially after sitting for a while or first thing in the morning. Your knee may feel tight and reluctant to move through its full range, then gradually loosen up with gentle activity.
Catching, Locking, and Giving Way
One of the most distinctive feelings of cartilage damage is a mechanical “snag” during movement. When the knee bends, you may feel it catch partway through the motion, as if something is briefly stuck. This happens when a flap of damaged cartilage or a loose fragment interferes with the smooth gliding surfaces inside the joint.
In more severe cases, the knee can fully lock, leaving you temporarily unable to straighten your leg completely. This usually means a piece of cartilage has broken free and wedged itself between the joint surfaces. The sensation is unmistakable: your knee simply refuses to extend, and forcing it causes sharp pain. Some people also experience the knee suddenly giving way or feeling unstable, particularly during weight-bearing activities.
Grinding and Crunching Sounds
As cartilage wears down, rough surfaces rub against each other instead of gliding smoothly. This produces a sensation called crepitus, a gritty, grinding feeling you can sometimes hear as well as feel. People describe it using words like grinding, grating, crunching, or crackling. It’s different from the occasional painless pop or click that healthy knees sometimes make. Cartilage-related crepitus tends to be continuous during movement rather than a single pop, and it often comes with discomfort.
Grinding under the kneecap is particularly common. Research using MRI has found that crepitus in the knee is significantly associated with cartilage lesions, bone spurs, and other structural changes in the joint between the kneecap and thighbone. In some cases, this grinding sensation is the earliest sign that cartilage is wearing down, appearing before more obvious pain or swelling develops.
Activities That Make It Worse
Cartilage damage announces itself most clearly during specific movements. Stairs are a classic trigger. When you climb or descend stairs, forces on the kneecap joint reach up to 3.5 times your body weight with each step. Descending is often worse than going up, because your quadriceps muscle has to work harder to control your descent, generating even higher forces across already damaged surfaces.
Squatting and kneeling compress the joint surfaces together and tend to provoke pain. Getting up from a low chair, crouching to pick something up, or sitting cross-legged can all be uncomfortable. Prolonged weight-bearing activities, like standing for long periods or walking on hard surfaces, can produce a deep ache that builds gradually. Many people notice they develop a limp after high-impact activities or long stretches on their feet, even if the knee felt fine at the start.
Swelling and Weakness
Swelling is common with cartilage damage, though it tends to be subtler than the dramatic puffiness you’d see after spraining a ligament. The knee may look slightly fuller than the other side, or you might just notice that it feels “tight” and harder to bend fully. This swelling comes from the joint producing extra fluid in response to irritated or damaged surfaces.
Over time, ongoing cartilage damage can lead to noticeable weakness in the quadriceps muscle on the front of your thigh. The muscle on the inner side of the thigh, just above the knee, may visibly shrink compared to your uninjured leg. This happens because pain and swelling cause the muscle to essentially shut down, a protective reflex that unfortunately makes the knee less stable and more vulnerable to further injury.
How Symptoms Change With Severity
Cartilage damage exists on a spectrum. In the earliest stage, the cartilage softens but remains intact on the surface. You might feel only occasional vague discomfort or mild stiffness, easy to dismiss as a “bad knee day.” At this point, there may be no catching or grinding at all.
As damage progresses, the cartilage surface develops cracks and fissures. This is when mechanical symptoms like catching and grinding typically begin, and pain becomes more consistent during loading activities. Swelling may come and go depending on your activity level.
In the most advanced stage, the cartilage wears away entirely, exposing the bone underneath. This produces more constant pain, significant stiffness, and pronounced grinding. The joint may feel larger or bonier than it used to, and activities that were once mildly uncomfortable become genuinely painful.
Cartilage Damage vs. a Meniscus Tear
These two injuries share many symptoms, which is why they’re easy to confuse. Both cause pain that localizes to one side of the knee or spreads through the joint, and both can produce catching or locking sensations. The overlap is real: many people have both injuries at the same time.
That said, meniscus tears tend to produce sharper, more localized pain along the joint line (the crease on either side of your knee), especially with twisting or pivoting motions. The locking from a meniscus tear is often more sudden and dramatic. Cartilage damage on the joint surface, by contrast, tends toward that vaguer, deeper ache with more gradual onset, and the grinding sensation is more prominent. Meniscus tears also commonly cause pain with deep knee bends and squatting in a way that feels like something is being pinched inside the joint.
Neither condition can be reliably diagnosed by symptoms alone. An MRI is typically needed to see the extent and location of the damage, since the sensations overlap so much between different types of knee cartilage injury.