A bruised knee can be painful, and because this condition is typically the result of some type of stress or injury, it can occur with or without further knee injury. Sometimes referred to as a patellar contusion, it is the result of blood vessels beneath the surface of the skin being damaged and leaking blood. The signs of a bruise may range from discoloration on the surface of the skin to swelling and tenderness to the touch.
Normally, the bruising that occurs because of minor bumps or impact trauma is called subcutaneous bruising and is marked by mild to moderate discoloration of the area and possibly mild pain or tenderness upon touch. This type of bruising is usually acute, or temporary, and should heal itself and disappear within a few days. An injury like this that results from minor impact may hurt briefly, but it is normally not cause for alarm.
Periosteal and intramuscular bruising is typically more painful than a subcutaneous bruise and is the result of a more severe impact or trauma, such as what might occur with a sports injury. A bruise that occurs to the bone is called periosteal, while intramuscular bruising is bruising of the muscles. A bruised knee can result in one or both types of bruising, and while the tell-tale discoloration may be present, pain, swelling, and discomfort when moving and touching the knee is also a sign of injury.
Sometimes, a bruise on the knee is a secondary symptom of a more serious injury. Bruising can occur during dislocation and even fracture of the patella, or kneecap. An injury this serious would normally be evident by marked pain, discomfort, and swelling. Treatment for any painful knee injury should be sought and stress should not be placed on the injured joint until a medical professional has diagnosed the injury and provided instructions for treatment and recovery.
It is possible for other forms of stress besides impact or injury to cause a bruised knee. Stress can be placed on the knees by excess weight and previous knee injuries are susceptible to bruising, especially during the healing process. Regardless of the cause, the signs are usually present in the form of pain, tenderness, swelling, and discoloration. Ice is an good early form of treatment for reducing swelling and temporarily relieving pain. Individuals should avoid taking aspirin or anti-inflammatory drugs unless prescribed by a medical professional as these can increase blood flow. Knee injuries that cause pain with movement or immobility should be evaluated by a healthcare provider as soon as possible.