- chondromalacia patellae (CMP)
Runner's knee is a condition causing pain in the front of the knee. It is often due to excess wear on the underside of the kneecap. It is also called chondromalacia patellae, or CMP.
What is going on in the body?
When the knee is bent and straightened, the kneecap glides back and forth over the end of the femur, or thighbone. The underside of the kneecap is in contact with the femur. Like the rest of the knee joint, this surface is covered with cartilage. Too much stress between the kneecap and the femur can damage the cartilage. The joint surface becomes softened and roughened. This wear causes joint irritation and pain.
Sometimes the joint swells because it produces extra fluid to improve lubrication. The contact pressure between the kneecap and femur varies according to activity. Deep knee bends exert a force equivalent to five times the body weight. Climbing stairs is equivalent to three times the body weight.
What are the causes and risks of the condition?
Runner's knee is usually caused by overuse when joggers run too long, too fast, or up too many hills.
Conditions that cause the knee to be poorly aligned can contribute to extra stress on the kneecap. These include knock-knee, outward rotation of the lower leg, or inward rotation of the thighbone.
Tight quadriceps muscles can also increase the pressure on the kneecap.
What can be done to prevent the condition?
Stretching exercises are good for prevention of runner's knee, particularly those exercises designed for the quadriceps muscles. A moderate training program should avoid stress on the knee. Excessive distance, speed, and hills should be avoided.
Orthotics, or arch supports, may help to reduce pronation of the foot.
How is the condition diagnosed?
Diagnosis of runner's knee begins with a history and physical exam. Joint X-rays are usually normal.
The healthcare professional may do an arthroscopy which is a surgical procedure in which a small, lighted tube is inserted into the joint so the joint can be examined.
Long Term Effects
What are the long-term effects of the condition?
Long-term effects of runner's knee are rare. If overuse continues and symptoms are ignored, arthritis
is a possibility.
What are the risks to others?
Runner's knee is not contagious, and poses no risk to others.
What are the treatments for the condition?
Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (i.e., Advil, Motrin) or naproxen (i.e., Aleve, Anaprox, Naprosyn), may be taken. The healthcare professional will also outline some activity limitations.
What are the side effects of the treatments?
NSAIDs may cause stomach upset or allergic reaction.
What happens after treatment for the condition?
Proper training, preparatory stretching, and activity limitations should be continued. Orthotics, such as arch supports, may be recommended.
How is the condition monitored?
The effects of the running program on the knee are monitored. Any new or worsening symptoms should be reported to the healthcare provider.