Pain in the knee is a very common complaint and can affect any age group. The knee is one of the largest and most complex joints in the human body, and impaired knee function results in limited mobility, difficulty in performing activities of daily living, and it reduces participation in sports.
The knee joins the thigh to the leg and is essential for normal movement. The knee joint has two components – the tibiofemoral joint (articulation between the thighbone and shinbone) and the patellofemoral joint (articulation between the kneecap and the thighbone). These joints get stability from multiple ligaments with additional stability provided by the surrounding muscles. The tibiofemoral portion also has a meniscus on each side and these menisci act as shock absorbers, help to stabilize the knee and protect the cartilage from damage.
There are multiple possible causes of knee pain but the acute (sudden onset) knee injuries are those which are feared most by sportsmen. These injuries may be traumatic or non-traumatic in origin and can involve ligament, meniscus or tendon tears, joint dislocations, cartilage injury or fractures. These injuries can end sporting careers and put a sportsperson at risk of early onset of arthritis in the knee.
Common causes of non-acute knee pain include:
· Osteoarthritis (OA)
· Patellofemoral pain syndrome
· Osgood-Schlatter disease in adolescents
OA is a progressive disorder of the joints which leads to degeneration of the cartilage and new bone formation at the surface and margins of the joints. Risk factors for OA in the knee include age, genetics, joint disorders in childhood, metabolic disorders, prior injury and obesity. Symptoms of knee OA include pain with activity, stiffness after resting and impaired mobility. As the condition progresses, deformity of the knee is usually noted.
Patellofemoral pain syndrome refers to pain in and around the patella, the kneecap. The patella moves within the trochlea (groove) of the femur when the knee is bent. This movement is controlled by the muscles of the quadriceps attach to the upper part of the patella.
Activities such as climbing stairs can increase the force acting on the patellofemoral joint to as high as eight times a person’s bodyweight. Factors which increase the force or affect how this force is distributed can lead to the patellofemoral pain syndrome. These include repetitive activities, biomechanical abnormalities of the femur, knee, tibia or foot, abnormal patella position, abnormally tight or loose stretched soft tissues, poor flexibility and poor muscle control. In addition to pain felt around the patella, other symptoms include aggravation by running, climbing stairs or prolonged sitting and cracking/creaking under the patella when moving the knee.
There are multiple tendons around the knee which can be affected by overuse, especially if combined with poor sporting technique. Patellar tendinopathy (jumper’s knee) is one of the most common tendinopathies in the knee and results from repetitive jumping activities and causes pain at the lower part of the patella. Other activities that result in other tendons being affected include repetitive acceleration and deceleration – as can occur in cycling and running – and repetitive downhill running.
Osgood-Schlatter disease affects the tibial tuberosity (bony prominence below the patella) in growing adolescents. The patellar tendon exerts a powerful pull on this bony area which has not yet fused to the tibia and leads to pain. Some children who are highly active during the period of rapid growth which occurs when puberty starts may suffer from this condition. The pain is localized to the affected area and is worsened by activity which leads to activity restriction- this varies from case to case.
The rehabilitation/sports medicine physician plays a vital role in the management of knee pain. This begins with a comprehensive evaluation, including history-taking and physical examination, to diagnose the cause of the pain. In some cases, imaging such as x-rays, ultrasound or MRI may be needed to confirm the diagnosis.
Once the condition is diagnosed, patient education can begin and the individualized treatment plan can be created. This will usually include an exercise programme which may be led by a physical therapist or by the patient. Pain control is essential and this would be achieved by avoiding aggravating activities and use of oral or injected medications as necessary. In cases of severe OA, or if otherwise indicated, a referral for surgery would be made.
Knee pain which is not improving after a short period of relative rest and pain medications, or which is worsening, should be evaluated. This will help accelerate the process of returning to optimal physical function.