Why Do I Have a Dent in My Knee? Common Causes

A dent or indentation around the knee usually comes from a loss of soft tissue rather than a problem with the bone itself. The tissue that fills out the contour of your knee includes muscle, fat, tendons, and bursae, and when any of these shrinks, tears, or shifts, the surface can look scooped out or uneven. The causes range from something as simple as muscle wasting from inactivity to rarer conditions like connective tissue disorders or congenital skeletal differences. Which cause applies to you depends a lot on where exactly the dent sits, how quickly it appeared, and whether you have pain or weakness alongside it.

Muscle Wasting Around the Kneecap

The single most common reason people notice a dent near their knee is atrophy of the quadriceps muscle, particularly the inner portion that sits just above and to the inside of the kneecap. This muscle bulk is what gives the area above the patella its rounded, filled-out look. When that muscle wastes, the skin sinks inward and a visible hollow appears. It can happen after an injury that kept you off your feet, after knee surgery, or simply from prolonged inactivity or disuse. People who sit at a desk for long stretches and do little leg exercise sometimes notice the indentation develop gradually on both sides.

Aging also plays a role. As you get older, you naturally lose muscle mass, and the quadriceps are among the first muscle groups to thin out. If the dent sits above the kneecap and is roughly symmetrical on both legs, muscle atrophy is the likeliest explanation. The good news is that targeted strengthening exercises, especially those that load the inner quad, can usually restore much of the lost bulk over weeks to months.

Fat Loss and Fat Necrosis After Trauma

A blow to the knee, a hard fall, or even a minor but direct impact can damage the layer of subcutaneous fat beneath the skin. When fat cells are crushed or their blood supply is disrupted, they can die off in a process called fat necrosis. The damaged fat doesn’t always rebuild. Instead, the body may replace it with scar tissue or simply reabsorb the dead cells, leaving behind a sunken area, a firm lump, or both. Fat necrosis and lipoatrophy have been documented after falls, blunt injury, surgery, and even minor procedures or injections.¹

Sometimes the aftermath is more complex than a simple dent. One case report described a patient who developed multiple subcutaneous lumps on the knee six months after a relatively low-speed trauma. Ultrasound imaging confirmed post-traumatic fat necrosis that had evolved into nodular cystic lesions beneath the skin.² These lumps can feel hard and sometimes sit right next to a visible depression, making the knee’s surface look uneven.

A related injury worth knowing about is a Morel-Lavallée lesion, which happens when a shearing force separates the skin and fat layer from the deeper tissue. This creates a pocket that fills with blood, lymph, or necrotic fat. While these lesions are most often described at the hip and thigh, the prepatellar region of the knee is also a documented site.³ If untreated, a Morel-Lavallée lesion can leave a permanent contour change once the fluid is reabsorbed or drained.

Dents Caused by Corticosteroid Injections

If you’ve had a steroid injection in or near the knee, the dent you’re seeing may be injection-related lipoatrophy. Corticosteroids are powerful anti-inflammatory drugs, but one well-known side effect is that they can cause fat cells near the injection site to shrink or die. The result is a localized depression in the skin that can appear weeks to months after the shot. A study of patients with localized lipoatrophy found that more than half had received intramuscular or intra-articular corticosteroid injections in the affected area before the depression developed.¹

One case report documented a patient who developed pain, tissue atrophy, and even skin color changes after a corticosteroid injection for pes anserine bursitis, a common condition treated at the inner side of the knee.⁴ The dent in that case was accompanied by visible depigmentation, making the area look both sunken and lighter than surrounding skin. Steroid-induced lipoatrophy sometimes resolves on its own over many months, but in other cases the fat loss is permanent. If you suspect this is the cause, mention it to your doctor before agreeing to another injection in the same spot.

Quadriceps and Patellar Tendon Tears

A sudden, dramatic dent that appears just above or just below the kneecap, especially after a stumble or a hard landing, could signal a tear in the quadriceps tendon (above the patella) or the patellar tendon (below it). When either of these thick bands of tissue ruptures, the kneecap is no longer anchored in its usual position. It may ride upward or downward, and the gap left behind is palpable as a soft, hollow indentation.

A meta-analysis of bilateral quadriceps tendon rupture cases found that a palpable gap above the kneecap was the most frequently reported physical finding, present in about 70% of documented patients. Swelling and an inability to straighten the knee were the other hallmarks, though the full classic trio of symptoms appeared in only about 58% of cases.⁵ That means a tendon rupture can be missed if the provider focuses only on swelling and doesn’t check for the gap. Missed or delayed diagnosis is one of the main causes of poor outcomes with these injuries, because the torn ends retract further over time and become harder to repair surgically.⁵

If you notice a new dent right above the kneecap and you can’t straighten your leg against gravity, that’s a reason to seek medical attention the same day. This is one scenario where the dent itself is a diagnostic clue, not just a cosmetic concern.

Scarring and Adhesions After Knee Surgery

People who have had arthroscopic knee surgery sometimes develop visible indentations at or near the portal sites where the instruments entered. The scar tissue that forms beneath the skin doesn’t always sit flat. It can tether the skin to deeper layers, pulling the surface inward and creating a dimpled or puckered look. In some cases, the scar tissue also restricts how the skin and soft tissue slide over the kneecap during movement, which makes the dent more prominent when you bend or extend the knee.

One case report described a patient who, after arthroscopic knee surgery, had pain in the scarred area along with restricted patellar mobility and a deficit of about five degrees in full extension. Dynamic ultrasound showed that the scar tissue was preventing normal tissue gliding.⁶ In that case, an ultrasound-guided injection of fluid to release the adhesion improved both the range of motion and the tissue sliding. If your dent sits right on an old surgical scar and feels tethered when you move the knee, adhesion-related tethering is worth investigating.

Post-surgical dents are also common after ACL reconstruction, total knee replacement, and open procedures that require larger incisions. The amount of visible indentation tends to depend on how much subcutaneous fat was present before surgery and how aggressively the scar contracts during healing.

Structural and Developmental Differences

Not all knee dents develop over time. Some people are born with structural variations that make the front of the knee look different from what they see on other people. Trochlear dysplasia, where the groove that the kneecap rides in is shallower or differently shaped than typical, can give the knee an unusual contour. An MRI-based study found an association between abnormal trochlear shape and severe cartilage problems in patients younger than 40, which means the structural difference isn’t always just cosmetic.⁷

A rarer but more distinctive condition is Nail Patella Syndrome, a genetic disorder that affects roughly one in 50,000 people. Its hallmark signs include abnormally small or absent kneecaps, dystrophic fingernails, and bony projections on the pelvis called iliac horns. The underdeveloped kneecaps can make the front of the knee look flat or scooped out, and patellar instability is a common complaint.⁸ If you’ve always had a dent in the knee area and also notice that your thumbnails are small, ridged, or partly absent, this condition is worth raising with a doctor. It can also involve kidney problems that benefit from monitoring.

Skin and Connective Tissue Conditions

A less common cause of a dent around the knee is localized scleroderma, also called morphea. In this autoimmune condition, patches of skin and the tissue layers beneath it become thickened and tight. Over time, the affected area can lose its normal fat and develop a groove or depression. An MRI study of patients with localized scleroderma found that about three-quarters had musculoskeletal involvement, with fascial thickening detected in 60% and subcutaneous septal thickening in 65%.⁹ When scleroderma hits near a joint like the knee, the combination of skin tightening and fat loss can produce a visible indentation that worsens gradually.

Other connective tissue conditions, including lupus profundus (a form of lupus that attacks subcutaneous fat) and panniculitis (inflammation of the fat layer), can also produce depressions in the skin of the legs, though the knee specifically is not the most common location. The distinguishing feature of these conditions is usually that the dent comes with skin changes like discoloration, hardening, or a shiny texture that feels different from the surrounding area.

When the Dent Is Actually a Bump Next Door

Sometimes what looks like a dent is actually normal tissue sitting next to a swollen area that has raised the surrounding surface. A Baker’s cyst behind the knee, a swollen prepatellar bursa in front of the kneecap, or even a meniscal cyst along the joint line can create enough local swelling that the adjacent area looks sunken by comparison. The dent in these cases is an illusion. Once the swelling is treated, the contour evens out.

This distinction matters because treating the “dent” is pointless if the real problem is the neighboring bump. If you notice the dent appeared around the same time as swelling elsewhere on the knee, consider that the indentation might resolve once the swelling does.

How Doctors Figure Out the Cause

Your doctor will start with a physical exam, feeling the area to determine whether the dent involves muscle, fat, tendon, or bone. They’ll check for warmth, skin changes, and whether the indentation is fixed or moves when you flex the knee. The location of the dent narrows the list considerably: above the kneecap points toward muscle or tendon, below the kneecap toward the patellar tendon, and on the sides toward fat-pad or bursal issues.

If imaging is needed, both ultrasound and MRI have roles. A comparative study found that ultrasound was more sensitive than MRI for detecting patellar tendon problems and prepatellar bursitis. MRI, on the other hand, was substantially better at identifying cartilage defects and structural problems like trochlear dysplasia.¹⁰ In practice, your doctor may order ultrasound first because it’s quick and inexpensive, then follow up with MRI if the picture is unclear or if bone and cartilage need a closer look.

One advantage of ultrasound is that it can be done dynamically, with the technician watching in real time as you bend and straighten the knee. This is especially useful for spotting scar adhesions or tendon problems that only show up with movement.

Dents That Go Away on Their Own

Many knee dents are not permanent. Muscle atrophy reverses with consistent exercise. Steroid-induced lipoatrophy sometimes fills back in over six to twelve months as the local steroid effect fades. Post-traumatic fat necrosis can remodel over time, though the speed varies wildly. Even some post-surgical adhesions soften as the scar matures, especially if you’re doing regular range-of-motion work.

The dents that tend to stick around are those caused by structural conditions like trochlear dysplasia or Nail Patella Syndrome, severe tendon ruptures that weren’t repaired, and deep scar tissue that has fully matured. If your dent has been stable for more than a year with no other symptoms, it has likely settled into its final form, and any further change would need medical or surgical intervention. That said, a persistent painless dent in an otherwise functional knee is, for most people, a cosmetic concern rather than a medical one. The time to push for answers is when the dent comes with pain, weakness, instability, or skin changes that suggest something more than simple tissue loss.