A knee bruise occurs when a forceful impact to the area causes small blood vessels under the skin to rupture. This damage releases blood into the surrounding soft tissues, which creates the familiar discoloration and swelling. While most knee contusions are minor injuries, the time it takes for them to completely resolve is quite variable, depending on the injury’s depth and severity.
The Typical Healing Timeline
A simple, superficial bruised knee usually begins to clear up within a few days, with full resolution often occurring in two to four weeks. The most visible sign of healing is the bruise’s color progression. Initially, within the first 24 to 48 hours, the bruise typically appears red, blue, or purple as the hemoglobin in the blood is still oxygenated and fresh beneath the skin’s surface.
As the body starts to metabolize the blood, the hemoglobin is converted into other compounds, causing the color to shift. Around the fifth to tenth day, the bruise will begin to turn a greenish shade due to the presence of biliverdin. This green color transitions to a yellow or brownish hue after about ten to fourteen days as the biliverdin is further broken down into bilirubin and then hemosiderin. The bruise is considered fully healed when the discoloration completely disappears.
Factors Influencing Recovery Speed
Recovery speed is influenced by the extent of the initial trauma. A superficial bruise involving only the skin and subcutaneous tissue will heal much faster than a deep muscle contusion or a bone bruise, which can take four to six weeks or even several months for full resolution. A bruise directly over the patella (kneecap) or on the bone itself tends to be more painful and slower to heal than one on the surrounding soft tissue.
Age also plays a role in the body’s natural repair mechanisms, as older adults generally experience a slower healing rate compared to younger individuals. A person’s general health and the use of certain medications can also affect the timeline. For instance, individuals taking blood-thinning medications may experience more extensive initial bruising and a slightly prolonged period for the blood to be reabsorbed.
Managing the Bruised Knee at Home
The R.I.C.E. protocol—Rest, Ice, Compression, and Elevation—is the standard for initial home care. Resting the knee involves avoiding activities that cause pain or place excessive stress on the joint.
Applying a cold compress or ice pack for 15 to 20 minutes several times a day helps to constrict blood vessels, minimizing swelling and internal bleeding. A light compression bandage can be used to further reduce swelling, but it should not be wrapped so tightly that it causes numbness or increased pain. Elevating the leg above the level of the heart uses gravity to assist in draining excess fluid from the injury site. Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) may be used to help manage pain and inflammation.
When to Seek Medical Attention
Certain warning signs indicate the injury may be more severe than a simple contusion. An inability to bear weight on the leg or a feeling that the knee is unstable or giving way suggests potential damage to a ligament or a fracture. Rapidly increasing or severe swelling, particularly if it happens immediately after the injury, may signal internal bleeding or a more significant structural issue.
Seek professional evaluation if the knee appears deformed or if you experience numbness below the injury. Signs of infection, such as fever, red streaking spreading from the bruise, or the area becoming unusually warm and painful, require prompt medical attention. If the bruise shows no visible signs of improvement or fails to clear up even partially after two weeks, a doctor should examine the knee to rule out a deeper injury.