Your Online Health Information Site


Knee Pain


Knee pain is a common complaint in medicine. Due to the knee’s exposure, it is vulnerable injury. It is weight bearing and for his reason is at a higher risk when the patient is overweight.The knee is a complex structure with a medial (inside) and lateral (outside) compartment as well as a patellofemoral joint.

Ligaments are holding all of these structures together. In addition, a joint capsule and muscle tendons that are providing significant support to the knee. Knee pain can develop when any of these structures experience an injury. When there is pain in the knee, the patient usually starts limping as weight bearing may be painful and the range of motion is reduced. With inflammation the synovial pouches, called bursae, can contain fluid (called an “effusion”) as does the knee joint. This makes the knee cap disappear and the normal contours of the knee are missing. A lower back injury can also refer pain to the knee. Injuries to the hip, pelvis and in an adolescent even a slip in the femoral growth plate (“slipped femoral epiphysis”) can mimic knee pain as well.

Knee Pain

Knee Pain

In the following I will describe the most common knee conditions and their causes in more detail, how to diagnose and how to treat them.

Common Causes Of Knee Pain


Alignment problems bowlegs, knock knees

The two major alignment problems are the bowleg (genu varus) and the knock-knee (genu valgus).

Bowleg (genu varus)

For a period of time it is normal for a toddler to have bowlegedness. However, by about 18 months this normalizes on its own. If it persists, rickets (Vit. D deficiency) has to be ruled out. An orthopedic surgeon should be consulted as uncorrected genu varus leads to premature osteoarthritis and the need for total knee replacement later in life, which can be prevented by intervening at a young age. Bracing usually helps to normalize it, if not, corrective surgery might be needed in order to prevent premature osteoarthritis.

Knock-knee (genu valgus) 

This is not as common and usually peaks at age 3, then outgrows itself by age 9. It is more common in girls. If it persists, a referral to an orthopedic surgeon should be made as uncorrected genu valgus leads to premature osteoarthritis and the need for total knee replacement later in life, which can be prevented by intervening at a young age. There is a surgical stapling method available that can straighten out the malalignment (Ref. 3,p.2404).

Avascular necrosis (also called “osteochondritis dissecans”)

This condition tends to happen suddenly and occurs on one side, usually the medial aspect of a knee. It occurs often in knee of an elderly female. There are predisposing risk factors such as prior treatment with systemic corticosteroids, a history of lupus, alcohol abuse, history of sickle cell anemia or the hormone changes of pregnancy. Also, a history of deep sea diving with exposure to increased barometric pressure can often be found. Part of the bone and hyaline cartilage of the medial femoral condyle is cut off the circulation and dies off, but then gets regenerated. Technetium-99 bone scan or MRI scan can help in the diagnosis. Treatment consists of high tibial osteotomy or total knee arthroplasty (knee replacement), both of which would require a referral to an orthopedic surgeon (Ref. 4).


This knee condition has different names: carpenter’s knee, Baker’s cyst, prepatellar bursitis, Anserine bursitis.

Congenital knee problems 

When the ligaments are lax, hypermobility of the knee can become a problem.

Another not infrequent problem are congenital plicae. 

Growing pains 

In children growing pains are common during periods of growth spurts.

Growing pains are harmless, but can be very hard on the parent’s mind: they occur in the middle of the night in children who are in the middle of a growth spurt. The legs (and also the arms) are very painful, but this disappears very quickly upon treatment with massage. In the morning there is absolutely no pain and no loss of function. Examination a the doctor’s office is normal. Usually within a few weeks even the nightly aches and pains are disappeared (Ref. 2).

Inflammatory arthritis 

When arthritis and inflammation are coupled, inflammatory arthritis exists. Conditions like gout, osteoarthritis, RA, AS, psoriatic inflammatory arthritis can occur. 

Inflammatory arthritis is one of the traditional forms of arthritis that tends to lead to synovitis, which is swelling of the synovial lining of the knee joint. Tests to diagnose and treatments to deal with these conditions vary according to the underlying diagnosis.

Knee trauma

The most common ones are strain/sprain, meniscal tear, ACL tear, ligamentous tear, bone/cartilage injury

malignant bone tumors , osteosarcoma and others.

There are a number of malignant bone tumors, the most common around the knee are the osteosarcoma and the malignant giant cell tumor. Look forbone cancer“, where diagnostic tests and treatment of all these bone tumors are discussed.

Osgood-Schlatter disease

Osgood-Schlatter disease  is a condition that is inborn, but becomes significant, when athletically minded adolescents get injuries to the knee.

Septic knee arthritis

This knee condition is due to bacteria that multiply in the synovial fluid of the knee. The result can be a septic knee arthritis .

It presents with a red, hot, swollen knee. Culture and sensitivity tests of a synovial fluid sample shows growth of  mostly Staph. aureus, also streptococcal and gonococcal bacteria. 



Inflammatory Arthritis

The following are forms of inflammatory arthritis, which you can find under “Related Topics” below.

Gout and pseudogout
Osteoarthritis (degenerative arthritis)
Rheumatoid arthritis (RA)
Ankylosing spondylitis (AS)


1. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 157.

2. ABC of rheumatology, second edition, edited by Michael L. Snaith , M.D., BMJ Books, 1999. Chapter 4.

3. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 270.

4. Wheeless’ Textbook of Orthopaedics:

5. Goldman: Cecil Textbook of Medicine, 21st ed.(©2000)W.B.Saunders

6. Ferri: Ferri’s Clinical Advisor: Instant Diagnosis and Treatment, 2004 ed., Copyright © 2004 Mosby, Inc.

7. Rakel: Conn’s Current Therapy 2004, 56th ed., Copyright © 2004 Elsevier

Last modified: April 18, 2021

This outline is only a teaching aid to patients and should stimulate you to ask the right questions when seeing your doctor. However, the responsibility of treatment stays in the hands of your doctor and you.