Anatomy of the Knee

The knee is a joint formed by the tibia (shin bone) and the femur (thigh bone) which are held in place by flexible ligaments. As the knee bends, the knee cap or patella (also a part of the knee) glides over the femur’s end. An articular cartilage covers the knee’s moving parts and is found on the bone edges. A space exists between the tibia and femur and between the patella and femur which is occupied by the cartilage. An x-ray of the knee will show the space but not the cartilage as it is not visible on the x-ray images.

Knee diseases

The cartilage can be damaged leading to a condition referred to as arthritis. Arthritis is literally a joint inflammation, but can be used to describe conditions in which cartilage damage occurs. The knee experiences synovial inflammation which causes pain in the early stages. Extensive cartilage damage causes pain due to the friction brought about by the knee bones rubbing against each other.

Diseases associated with the knee include the following:


It damages the cartilage but is also associated with inflammation. It mostly affects joints in the leg but doesn’t affect internal organs. Its cause is not clearly understood, though it has been associated with “wear” and “tear.” However, there are some predisposing factors to the condition which include;

  • A previous joint fracture
  • Torn ligaments/menisci
  • Abnormal knee bones development

Osteoarthritis of the knee is associated with a thin or completely absent cartilage which makes the knee bones grind against each other whenever there is movement. The grinding brings about mechanical pain. Similarly, pain may also be brought about by inflammation due to floating cartilage in the joint. Diagnosis of the condition is through x-rays rather than blood tests.

Rheumatoid Arthritis (R.A)

This inflammatory condition originates in the synovium and eventually destroys the joint cartilage as well as the bone adjacent to the cartilage. Its cause is not yet known. It affects several joints simultaneously as well as internal organs. Diagnosis is also by x-ray which shows the bone density loss. Blood tests can also be done–though they are very unreliable–by measuring rheumatoid factor. Rheumatoid factor is present in 80% of affected individuals’ blood who have had the condition for over 18 months. In early stages of the condition, the rheumatoid factor is much less. On the other hand, approximately 7% of people over 70 years of age show positive results for rheumatoid factor even if they don’t suffer from the condition. This makes blood tests very unreliable for diagnosing the condition.


Osteonecrosis is a rare condition that occurs when the knee bones lose blood supply, making them eventually die and collapse, causing significant pain. Its cause is also not known but some predisposing factors include;

  • Alcoholism
  • Joint injuries
  • Extensive steroid treatment

Another source of pain in the knee is due to damage of the meniscal cartilage, other than articular cartilage. It’s a disc cartilage separate from the tibia, femur and the patella. There are two meniscal cartilages in the knee sandwiched between the tibia and the femur. Injury to these cartilages is mostly associated with athletics. A torn meniscal cartilage will not heal but remains in abnormal positions of the knee and oozes out fluid that eventually cause pain upon twisting. An arthroscopic surgery can be done to remove the torn cartilages. On the other hand, an arthroscopic surgery cannot correct the problem of a worn out articular cartilage. In such a situation, a knee replacement is usually the best alternative.

Other symptoms associated with knee arthritis include;

  • Creaking
  • Catching
  • Decreased walking distance due to pain
  • Swelling
  • Painful limps
  • Buckling
  • Locking
  • Failure of the knee to fully straighten or bend

At St Pete Hip and Knee clinic, you will get professional help in dealing with conditions of the hips and knees from experienced staff and doctors. At the clinic, you will get professional orthopedic services to help you get proper treatment and prevent diseases and injuries of the musculoskeletal system, as well as faster recovery and return to a younger and active lifestyle through minimally-invasive surgery. In addition, the clinic performs implant design and testing, as well as total hip and knee replacement surgery so that you can lead an active lifestyle once again.

Kurt Hirshorn MD of St Pete Hip and Knee guarantees expertise and compassion when caring for his patients, and ensures a good hospital stay. Schedule an appointment today or call us at (727) 755-0313.

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4600 4th Street North
St Petersburg, FL 33703, USA
Phone: (727) 755-0313

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St Pete Hip and Knee | 4600 4th Street North, St Petersburg, FL 33703 | Phone (727) 755-0313
Kurt C. Hirshorn, MD, MPH | Copyright (c) 2019