Introduction
Anatomy
Cause
Symptoms
Diagnosis
Non-surgical treatment
Surgical treatment
Rehabilitation
Prevention
Anterior knee pain is a common problem in active adolescents and young adults, though it can affect people of any age. It is characterised by pain perceived in the anterior region of the knee.
The knee is the largest joint in the body. Normal knee function is required to perform most everyday activities. The knee is made up of the lower end of the thigh bone (femur), which rotates on the upper end of the shin bone (tibia) and the kneecap (patella), which in turn slides in a groove on the end of the femur. The joint surfaces where these three bones touch are covered with articular cartilage, a smooth substance that cushions the bones and enables them to move easily.
The frequency of anterior knee pain is related to the considerable compression and sheer forces that are transmitted through the patellofemoral joint (the joint between the kneecap and the thigh bone). Whether the pain is originated from the underlying damaged cartilage is a subject of debate since the articular cartilage is devoid of nerve endings. While no specific etiology has been defined, signs and symptoms are variable and multiple tissue sources and may exist. In general, it is believed that anterior knee pain is caused by an imbalance of the muscle forces around the knee cap, causing it to pull laterally and produce abnormal stresses underneath the kneecap. Other distinct causes for the pain include overuse, trauma, abnormal bony structure with or without kneecap instability, tightness, imbalance or weakness of thigh muscles or misalignment of the lower limbs. However, in many instances, the cause is obscure.
As the name implies, the pain usually arises in the anterior region of the knee joint. The pain is usually mechanical, exacerbated by activity, especially during stairs climbing, squatting or kneeling, and relieved by rest. Swelling may occur as a result of the underlying inflammation.
An orthopaedic surgeon will examine the patient with anterior knee pain to identify possible causes, including any misalignment of the lower limbs, thigh muscle strength and flexibility, heel cord tightness or any other feet abnormalities. X-ray can be taken to rule out any possible structural damage to the knee joint. Your surgeon may proceed to perform other more specific investigations such as CT scan or MRI to delineate the exact pathology depending on the clinical situation.
Treatment depends upon the particular problem causing knee pain, and is usually non-surgical. Initial treatment should consist of rest and swelling control modalities. After that, the usual treatment is a trial of exercise. This usually consists of closed chain quadriceps exercises such as cycling, combined with hamstring stretching and other exercises depending on what is found in the physical exam. The majority of patients who have pain in the anterior knee structures usually will respond to this type of physical therapy or exercise regime. Medications including the use of anti-inflammatory drug may help alleviate the symptoms. In case none of the above-mentioned methods help, a re-evaluation is necessary to determine if a change in therapy or surgical treatment methods can solve the problem.
Surgical treatment may be necessary if conservative treatment fails and the underlying pathology of the anterior knee pain could be identified. Release of the tight tissue on the kneecap or surgical corrections of the underlying abnormal bony structure are some of the surgical options in managing persistent anterior knee pain.
During rehabilitation after the surgery, it is important to perform exercises that help to strengthen the quadriceps muscle and regain hamstring flexibility. After the pain and swelling subside, you may need to train your knee to gradually regain its normal range of motion, strength and endurance according to advice given by an orthopaedic surgeon or physiotherapist.
Your orthopaedic surgeon may advise you on appropriate shoe wear to correct any underlying feet abnormality that may be related to your anterior knee pain. To prevent injuries, always warm up with stretching exercises before any strenuous activities. Limit the duration of activities, especially those requiring repeated bending of the knee joint if your symptom persists. Regular and an adequate amount of muscle strengthening exercises for the knee without excessive pressure on the joint, such as swimming and cycling, may help to prevent the symptoms.
Dr. CHAN, Wai-lam