Knee pain

• What is knee pain?
• Statistics
• Risk factors
• Progression
• Symptoms
• Clinical examination
• How is it diagnosed?
• Prognosis
• Treatment
• References

What is knee pain?

Knee pain can result from injuries to the knee or hip.
The knee joint is composed of three articulating bones – the femur (thigh bone), tibia (shin bone) and patella (knee cap). These bones are held together by ligaments and the quadriceps muscle helps with stability. The joint, like other joints in the body is lined with cartilage, but in addition, it also has menisci which help to mould the surfaces of the knee joint so they can articulate more favourably and help to provide some lubrication. The joint is also surrounded by several bursae – fluid filled compartments which help with lubrication between the different structures.
Knee pain can result due to injury to any of the above structures. Pain due to knee problems is commonly felt at the front of the joint. Knee pain can also result from hip problems which can often provide a diagnostic challenge.

Statistics of knee pain

Knee pain on the whole is a very common condition and frequent problem presenting to general practitioners. The overall prevalence of knee pain in the population is approximately 19%. The incidence increases steadily with age. Furthermore, the severity of the pain increases with age and a greater percentage have pain associated with disability.

Men

It is estimated that the overall prevalence of knee pain for men of all ages is between 15 and 20%. A study in the US showed that approximately 18% of men aged 60 years and older reported knee pain and the incidence increases steadily with age. Similar proportions of Australian men are expected to be affected. The highest prevalence of knee pain was reported in men 85 to 90 years old at nearly 24%.

Women

The incidence of knee pain has been found to be slightly more common in females compared to men. The overall prevalence of knee pain in women is approximately 20%. A study in the US showed that approximately 23% of women aged 60 years and older reported knee pain. Similar rates are expected to occur in australian women. There was a trend for the reports of knee pain to increase consistently with age. The highest prevalence of knee pain was reported in women 85 to 90 years old at approximately 30%.

Children

Knee pain, particularly chronic knee pain is less common in children due to reduced incidence of degenerative joint disease. The total prevalence of chronic knee pain in adolescents is around 18% compared to approximately 4% in children. There is no significant difference in the prevalence of chronic knee pain between boys and girls in these age groups. Adolescents are more prone to bone pain than children due to rapid growth of articular structures during this period.

Risk factors for knee pain

The most common causes of knee pain are:

• Ligament strains and sprains. For example, you may often hear them saying a football player has torn his medial collateral ligament. This basically means the ligament stabilising the inside of the knee is torn due to a blow to the outside of the leg.
• Osteoarthritis which is a degenerative joint disease often affecting the knee joint. This is more common in elderly patients.
• Patello-femoral syndrome (anteriour knee pain)
• Overuse syndromes – tendinitis, bursitis, which refer to inflammation of the tendon and bursa (fluid filled bags that reduce friction) respecively. Wear and tear can damage these structures and cause inflammation.
• Osgood-Schlatter disorder – an overuse problem where the quadriceps tendon causes inflammation due to excessive traction on the tibial tubercle where it attaches. This is more common in athletic adolescents.
• Fractures around the knee
• Gout and pseudogout
• Osteochondritis dissecans: a small fragment of bone detaches from the lateral part of the femoral condyle (joint surface) – it gives rise to pain, as well as ‘locking’ and the sensation of the knee ‘giving way.’
• Overweight and obese patients have a higher incidence of knee pain presumably due to the increased pressure on the joint.
• Referred pain from the hip, femur, or spine.

Some conditions are serious, and should not be missed:

• Anteriour cruciate ligament tear
• Serious infections: septic arthritis (infection of the joint), or osteomyelitis (infection of the bone).
• Neoplasms:secondary or primary bone cancers.
• Rheumatoid arthritis and other inflammatory disorders.
• DVT’s

Children

Knee pain in children and adolescents is commonly due to the following conditions:

• Patella sublaxation- which refers to loosening of the patella and the patient feeling like the knee is ‘giving way.’ This condition is more common in young girls.
• Osgood-Schlatter lesion- There is localised pain at the tibial tuberosity where the quadriceps muscles insert. The typical patient is a 13- or 14-year-old boy (or a 10- or 11-year-old girl) who has recently gone through a growth spurt.
• Patellar tendonitis- inflammation of the patellar tendon that produces vague pain at the front of the knee worse when walking down stairs or running.
• Arthritis- bacterial, viral or inflammatory.
• Referred pain from the hip.
• Osteochondritis dissecans- where the bone and cartilage in the joint becomes calcified and may produce loose fragments of bone that can become caught.
• Tumours and malignancies are rare but they should always be considered.

Progression

Largely depends on the condition:

• Traumatic conditions such as ligament ruptures or meniscal strains occur after injury – often a twisting injury. A ‘pop’ is sometimes heard by the patient with ligament injuries after which swelling (bleeding into the joint) occurs immediately and the knee may give way. Swelling is usually delayed with meniscal injuries.
• Osteoarthritis is a chronic condition that causes pain and stiffness most days, usually worse after activity.
• Acute infections such as septic arthritis or osteomyelitis need urgent diagnosis because they can cause joint destruction as well as overwhelming sepsis if not treated.
• Overuse conditions such as bursitis, tendinitis and Osgood-Schlatter will often settle if you abstain from sporting activities for a period of time.

How is knee pain diagnosed?

Blood tests:

• Rheumatoid factor (RF) for Rheumatoid arthritis. This measures a specific antibody in the blood which is present in the majority of patients with Rheumatoid arthritis. However, several other conditions are also associated with elevated RF.
• Blood cultures for septic arthritis;
• Elevated ESR/CRP or white cell count will suggest inflammation/infection.

Imaging:

• X-rays of the knee (lateral, AP, and skyline) can pick up signs of osteoarthritis, fractures, and other obvoius conditions. They are not very helpful in soft tissue injuries (ligaments, meniscus), inflammatory conditions, and early on in Osteochondritis dissecans.

Prognosis of knee pain

This also largely depends on the condition:

• Small ligament strains, and overuse conditions will settle with rest.
• Anteriour knee pain in adolescence tends to settle with time.
• Osteoarthritis can not be cured, but multi-disciplinary management can help improve function and mobility and reduce pain. Knee replacement will help patients with severely limited mobility or pain.
• Inflammatory conditions can be progressive, leading to progressive joint destruction and loss of function, though aggressive treatment can hopefully prevent this. Most patients will have progressive disease that can lead to significant disabilities.
• Other conditions such as infections can be treated, though if treated late can also lead to joint destruction.
• Meniscal tears increase the risk of osteoarthritis in the future, regardless of treatment.

Treatment of knee pain

Treatment depends on the cause. Osteoarthritishas mutlimodal treatment including:

• Weight loss and sensible exercise are important. A walking stick may help mobility.
• Physiotherapy and Occupational therapy referrals to improve mobility, and advice on aids in the home and more efficient performance of daily functions.
• Simple analgesics such as NSAIDs and cox-inhibitors though stomach ulcers can occur with both.
• Alternative therapies: heat, massage, acupuncture, and glucosamine may be of help in relieving symptoms but do not alter disease progression.
• Joint injection of steroids can provide relief for severe episodes of pain.
• Finally, referral for surgery should be made for debilitating and intractable pain and disability – since total knee replacement can be of significant benefit in improving function.

Osteochondritis dissecans may require surgery for fixation of the loose fragment.
Septic arthritis and osteomyelitis require long-term antibiotics and often surgical drainage of the joint for septic arthritis.
Inflammatory conditions such as rheumatoid arthritis (RA) are also treated via a multidisciplinary approach involving physiotherapy, OT, rheumatology, medical and surgical aspects. Splints, rest and then rehabilitation are often used. Evidence now shows that RA is a severe and disabling condition with significant mortality from extra-articular manifestations, and it is recognised that early treatment (within 3-12 months of diagnosis) with disease modifying agents (in particular methotrexate) can retard progression of disease and even induce remission in some patients. Steroids, NSAIDs and analgesics are also used in these patients mainly for symptom management. In the late stages of disease joint replacement, tendon repairs and other surgeries are often indicated.
Mild ligament sprains and other soft tissue injuries may require nothing else but ice packs, rest and analgesics.
Severe ligament and meniscal tears may require surgical repair, especially in sports professionals or other very active people.

References

1. Anderson R, Anderson B. Evaluation of the adult patient with knee pain. Up-to-date, 2006.
2. Calmbach W, Hutchens M. Evaluation of Patients Presenting with Knee Pain: Part I. History, Physical Examination, Radiographs, and Laboratory Tests & Part II. Differential Diagnosis. Am Fam Physician 2003;68:917-22.
3. Kumar P, Clark M. Clinical Medicine. WB Saunders 2002.
4. Murtagh, J. General Practice. Second Ed. McGraw-Hill, 1998.
5. Paice E. Pain in the hip and knee. British Medical Journal. 1995. vol. 310, pp. 319-322.