Anatomy of the Knee

The knee joint is a complex joint which is actually three joints in one cavity. There are two joints between the thigh bone (femur) and the shin bone (tibia) and a joint between the thigh bone (femur) and the knee cap (patella). The complexity of the joint necessitates an experienced knee surgeon, such as Mr Gordon Shepard, to undertake diagnosis and treatment of any problems that arise with it.

The joint surfaces are covered in articular cartilage which provides the smooth surfaces on which motion at the joint occurs. The articular cartilage is so smooth that the friction at the surfaces is less than that of wet ice on ice. Arthritis is the degeneration of this cartilaginous lining.

Due to the shape of the articular surfaces, that is curved on flat, the joint is intrinsically unstable. It depends upon surrounding ligaments and muscles for it’s stability.

There are four main stabilising ligaments around the knee. The medial (inner) and lateral (outer) collateral ligaments connect the femur to the tibia and the fibula respectively down the outside of the knee. The anterior and posterior cruciate ligaments are within the knee and join the femur to the tibia in a crosswise manner (hence the name cruciate).

The main muscle groups around the knee are the quadriceps in front of the knee and the hamstrings behind the knee. The four quadriceps muscles join into a single tendon in which the patella lies. The patellar tendon (or ligament) then runs from the patella to the tibia in front of and below the knee. The hamstring muscles attach to the tibia on both the inner and outer sides and, with the calf muscles, form a diamond shaped area behind the knee called the popliteal fossa.

Between the femur and the tibia lie the two meniscal cartilages. These are c-shaped and they act as shock absorbers and help spread the load transmitted through the knee over a greater area. These are “the cartilages” that are commonly torn by sportsmen.

General Knee Information

Complications of knee surgery

Complications from knee surgery range from minor problems such as delayed wound healing to more serious problems such as deep infection, wound breakdown, nerve injury, blood clots (thrombosis), embolus, pain and death. Surgeons will do everything in their power to reduce the rate of complications such as using drugs to thin the blood or foot pumps to prevent clots and antibiotics to prevent infection. All major orthopaedic surgery should also be performed in ultra-clean air flow theatres to reduce the rate of infection.

However, despite the best efforts of the patient, the surgeon and the nursing staff, complications sometimes do occur. The vast majority of complications are not due to anything the surgeon has, or hasn’t, done but rather are recognised risks that surgery carries with it. The patient has a right to be aware of these risks and a responsible surgeon will discuss these risks fully with the patient prior to the patient consenting for surgery to be performed. If the patient feels the risks are unacceptable then they should refuse the surgery. A patient should not consent to surgery unless the surgeon is willing to discuss the risks to the patient’s satisfaction.

Treatment for knee problems

In general terms, treatment for knee problems can be divided into two main types, non-operative and operative.

NON-OPERATIVE TREATMENT

Many knee problems do not require surgery and can be cured or at least significantly improved by treatments such as physiotherapy. Such treatments require a lot of responsibility and commitment from the patient to be successful and sometimes patients have difficulty in making this commitment. However surgery is not the alternative to an inability to comply with a course of physio treatment.

Other problems may require even more simple remedies which may be equally unpalatable to a patient. A young person with early osteoarthritis of the knee may just need to alter his activities to see a significant reduction in symptoms but to a person who has played a particular sport for many years, retirement from the sport may be difficult. Another problem is obesity. When coming down stairs, the force on the kneecap is approximately 5 times body weight and therefore for people with arthritis or anterior knee pain simple weight reduction may significantly improve symptoms.

OPERATIVE TREATMENT

If non-surgical treatments are not appropriate or are not successful, then surgery is required. The chances of surgery being successful are greatly increased by having your surgery performed by someone with a special interest in knee surgery and by complying with the treatment and rehab regime as outlined by your surgeon and therapist.

Arthroscopy

Arthroscopic procedures are commonly referred to as “keyhole” procedures due to the fact they are performed through two, or occasionally three, small incisions in the skin over the knee. A small microscope is inserted into the knee and the surgeon can then confirm the diagnosis. Usually, but not always, a procedure can be performed that may cure or significantly improve the patient’s problem. Most arthroscopic procedures are performed as day case surgery.

The picture on the left shows a torn meniscal cartilage during an arthroscopy. The instrument is a probe used to define the tear and the tip is only 3mm long. Small tools and radiofrequency probes were used to remove the tear.

Open procedures

Problems outside the knee cavity and more major problems within it are not amenable to arthroscopic surgery. The techniques involved in open knee surgery range from minor day case surgery up to major undertakings such as total joint replacement which may require a stay in hospital for a few days.

Investigations for knee problems

X-Rays

The most common investigation to be performed are plain X-rays. X-rays are useful for looking at the bones in the knee joint but are not particularly useful for looking at the soft tissue parts of the knee. There are four common views that most knee surgeons would order: a front to back view with the patient standing, a side view, a view with the knee bent to look at the joint behind the kneecap and a view with the knee bent to look in the notch in the femur.

MR Scans

The next most common investigation is an MR (Magnetic Resonance) scan.  These scans are excellent for viewing the soft tissue components of the knee.  They are therefore good to visualise ligamentous injuries and injuries to the meniscal cartilages.  They also reveal bony pathology such as bone bruises, stress fractures and avascular necrosis.

CT Scans

CT (Computed Tomography) scans are less commonly used in the investigation of the knee since the advent of MR scanning.  However they are still very useful when the pathology is of bone and are especially useful in the management of complex fractures around the knee and in assessing the alignment of the knee in patello-femoral problems..  In conjunction with an injection into the joint, CT scans can be used to assess injuries to the lining cartilage of the knee.

Ultrasound scans

Ultrasound scans are sometimes used to investigate pathology of the patellar tendon and also to rapidly assess swellings around the knee.

Nuclear medicine scans

Scans such as technetium and indium scans are useful for the diagnosis of bone infection, occult fractures and tumours.  A small dose of a radioactive substance is injected into a patient and the substance attaches to bone.  In areas of high bone turnover, such as is found in infection, fractures and tumours, more radioactivity collects.  The patient is then scanned with a gamma camera which picks up the radiation and converts the information into a picture.

Wear and Tear problems

Problems that arise around the knee that are not as a result of acute injuries are often due to “wear and tear” or degenerative conditions. These often first affect people in middle age and may start with only minor problems.

The most common degenerative condition is the degeneration of the lining of the joint or osteoarthritis. However degenerative conditions can occur in many of the structures around the knee such as the patellar tendon and the cartilages ( menisci ).

As the name would suggest the nature of degenerative conditions is generally to worsen unless treated. Specific information regarding degenerative conditions can be found in the pathology section of this website. more content here.

Common injuries around the Knee

Sporting and work related injuries around the knee are very common. A recent study of injuries revealed that approximately 15% of all sporting injuries are sustained to the knee joint.

Knee injuries are often sustained following a twisting action and commonly contact is involved. The most well known injuries that require surgery are tears of the meniscal cartilages and anterior cruciate ligament rupture but not all people who twist their knees sustain these injuries or require surgery.

Any of the ligaments around the knee may be strained, the bones that make up the knee joint may be fractured (broken) and the tendons that move the knee may be strained or ruptured.

Serious injuries of the knee that may require medical attention usually cause significant swelling of the joint which is often obvious but may be more subtle and only be felt as an uncomfortable tightness in the knee. Immediate swelling of the knee (within 15 minutes) following an injury suggests either a fracture, an anterior cruciate ligament rupture or a major cartilage tear and the injured person should seek medical advice at the earliest opportunity.

Information regarding specific injuries can be found in the pathology section of this website.