A visible dent or indentation on or around the knee can be concerning. These can vary from subtle grooves to more pronounced concavities. While some knee indentations are harmless and reflect normal anatomy, others may indicate underlying conditions that warrant medical attention. Understanding the potential causes helps determine when observation is sufficient and when professional advice is beneficial.
Normal Variations and Common Causes
Many knee indentations are benign, stemming from the knee’s natural anatomy or common, non-serious occurrences. The knee joint is complex, featuring bony prominences, tendons, and muscle attachments that create natural depressions. For instance, the area just below the kneecap, where the patellar tendon attaches to the tibia, often presents as a slight groove, especially when the leg is extended or the quadriceps muscle is contracted.
Localized fat atrophy, also known as lipoatrophy, is another common cause for a visible dent. This condition involves the loss of subcutaneous fat, the layer of fat just beneath the skin. Fat loss can result from previous injections, particularly steroid injections for knee pain or inflammation, sometimes leading to a localized indentation at the injection site. Minor trauma, prolonged pressure, or natural fat redistribution with aging can also contribute to lipoatrophy and the appearance of a dent.
Muscles around the knee can also create temporary or subtle indentations. When muscles like the quadriceps flex, their bulk can make adjacent areas appear sunken. When they relax, underlying bony structures or natural depressions may become more prominent. Minor impacts or persistent pressure, such as resting a knee on a hard surface for an extended period, can sometimes lead to transient indentations without causing significant injury.
Underlying Medical Reasons
While many knee dents are harmless, some can point to medically significant underlying reasons. Muscle atrophy, the wasting away of muscle tissue, is one such reason. Significant disuse, such as prolonged immobilization after injury or surgery, can lead to a reduction in muscle mass, creating a noticeable dent where the muscle has diminished. Certain neurological conditions affecting nerve signals to muscles or severe, long-standing arthritis can also cause atrophy.
Connective tissue disorders represent another category of potential causes. These conditions affect tissues that support, connect, or separate other tissues and organs in the body. For example, localized scleroderma (morphea) can manifest as hardened, thickened skin patches that may appear sunken or dented due to changes in underlying collagen and fat. These conditions typically involve changes to skin texture or color in addition to the indentation.
In rare instances, a localized fluid collection or swelling, such as a cyst, might indirectly cause a dent. If pressure is applied nearby or the cyst resolves, it might leave a temporary impression. Post-surgical changes can also result in indentations. Scarring from incisions, localized tissue removal, or changes during a knee operation can lead to a permanent depression in the skin and underlying tissues.
When to Consult a Doctor
Consult a medical professional if a knee dent is accompanied by other symptoms or is concerning. Seek medical attention if the dent is associated with pain, swelling, redness, or warmth, as these signs could indicate inflammation, infection, or acute injury. A doctor should also evaluate any dent that limits the knee’s range of motion or is accompanied by numbness or tingling.
Consult a healthcare provider if the dent appeared after a significant injury, or if it is progressively growing larger or changing rapidly. The sudden, unexplained appearance of a persistent dent, without a clear preceding event like an injection or minor trauma, also warrants medical evaluation. Even if a knee indentation is medically harmless, some individuals may choose to consult a doctor for cosmetic concerns or reassurance. A medical professional can diagnose the cause through a physical examination and, if necessary, recommend appropriate diagnostic tests or management strategies.