The knee is the largest joint in the body and it is also one of the most complex. The knee joint is made up of four bones, which are connected by muscles, ligaments, and tendons. The femur is the large bone in the thigh. The tibia is the large shin bone. The fibula is the smaller shin bone, located next to the tibia. The patella, otherwise known as the knee cap, is the small bone in the front of the knee. It slides up and down in a groove in the femur (the femoral groove) as the knee bends and straightens.
Common Knee Conditions
Anterior Cruciate Ligament Injuries
The ACL is one of the main stabilizing ligaments of the knee. The ACL helps stabilize the knee by preventing excessive forward movement or rotation of the shin bone (tibia) on the thigh bone (femur). If the ACL is significantly damaged the knee can feel “unstable” or it may “give out”. Depending on the type and severity of the injury, other structures in the knee may be damaged in addition to the ACL. There may be injuries to the “shock absorbing” cartilage (menisci), the collateral ligaments (MCL or LCL), the posterior cruciate ligament (PCL) or to the bones of the knee. The degree of injury to the ACL may vary. In some cases the ACL may only be partially torn or in more serious cases the ACL may be completely torn. Unfortunately, the ACL does not have the ability to completely heal once it is injured.
The ACL may be injured in a number of ways but the most common mechanisms described are a twisting injury or a sideways blow to the knee. In most cases the knee will be painful, swollen, and/or feel unstable. If the ACL is the only structure damaged the initial injury may go unnoticed until the knee is subjected to twisting or rotational forces and the knee “gives out”, “gives way”, or “collapses”.
Examination techniques that detect looseness and rotational instability in the knee are effective in detecting ACL tears. X-rays are often done at the time of the injury to make sure that the bones of the knee are not broken. A special machine called an arthrometer or other tests such as Magnetic Resonance Images (MRI) are occasionally used to help diagnose ACL tears in difficult cases.
The treatment of ACL injuries depends on the severity of the injury and other associated injuries. Each treatment plan should be individualized. Initially protection (by use of crutches and/or a rehabilitation brace), rest, ice, compression and elevation (PRICE) of the injured knee will help reduce pain and/or swelling.
After an ACL injury the long term goal is to return the individual back to their previous level of activity. Achieving this goal will depend on the function and stability of the knee. A general knee rehabilitation program which includes strengthening exercises, flexibility exercises, aerobic conditioning, technique refinement and proprioceptive (biofeedback) retraining is the most important factor in improving knee function and stability. Stability may be improved by an ACL knee brace and/or surgery to reconstruct the ACL.
Even with the most ideal treatment the knee may never be as “normal” as the uninjured knee and modification of activity may be required. Furthermore, some research has identified that individuals who have repetitive episodes of giving way in their knee are at greater risk for further knee injuries and premature “wear and tear” arthritis (osteoarthritis) of the knee joint. However, doctors and physiotherapists trained in treating ACL injuries can outline an individualized treatment plan which will maximize the long-term function and stability of the knee.
To read more about ACL braces click here. Please visit the links section for additional information on ACL injuries. Links have been provided to other websites as well as online medical journals. Other knee injury topics can also be accessed.
Meniscus (Cartilage) Injuries
The meniscus is a “C” shaped “shock absorber” which lies between the thigh bone (femur) and the shin bone (tibia). There is a meniscus on the inner (medial) side of the knee and one on the outer (lateral) side of the knee. Injuries to either the medial meniscus or the lateral meniscus are common and are often referred to as a “torn cartilage”. Injuries to the menisci often result in pain and swelling in the knee. If the torn piece of meniscus is large, it may cause the knee to catch, lock, or give way (For more anatomy, click here).
Catching occurs when the torn fragment briefly lodges between the bones then works its way out. If the fragment does not work its way out the knee will remain “locked”, meaning the knee cannot fully bend or straighten. Locking can be brief (lasting seconds or minutes) or persistent (lasting weeks). Giving way occurs when the torn piece of meniscus slips out of place which causes pain and reflex relaxation of the thigh muscles. When the muscles relax the knee “gives way” or “gives out.”
The most common cause of sudden (acute) meniscal tears in younger people is a combined loading and twisting injury to the knee. However, the medial or lateral meniscus can undergo a degenerative tear without any significant injury to the knee. The medial meniscus is more frequently injured than the lateral meniscus.
Meniscal injuries are often associated with a ligament tear of the knee. An injury to one of the main supporting ligaments of the knee can result in an unstable knee increasing the chance of tearing a meniscus. When a meniscus is injured the knee often becomes painful and/or swollen. The pain is usually made worse by specific movements such as bending or twisting the knee. Certain maneuvers may produce a “click”, “pop” or sharp pain which is often localized to the medial or lateral joint line (the space between the thigh bone and the shin bone). Swelling can be caused from irritation of the knee joint by the torn meniscus.
X-rays cannot detect meniscal injuries but are useful to rule out wear and tear arthritis (osteoarthritis), loose pieces of bone or a broken bone which may mimic a “torn cartilage”. Occasionally a special test called Magnetic Resonance Imaging (MRI) is required. Arthroscopic surgery is helpful in both the diagnosis and treatment of these injuries.
Initially the treatment of meniscus injuries may include activity modification, ice, medication (to reduce pain and/or swelling) and physiotherapy. If a torn meniscus does not heal, and pain, swelling or intermittent catching persists, arthroscopic surgery may be necessary. Arthroscopic surgery is usually required if the knee remains locked.
The word arthritis means inflammation (swelling) of a joint. Osteoarthritis, also known as “wear and tear” arthritis is the most common type of arthritis. It is estimated that osteoarthritis affects one out of every ten people and that 85% of people over the age of 70 will have osteoarthritis. The knee is one of the most common joints affected by this disease.
Osteoarthritis affects the articular cartilage in the knee. Articular cartilage is the smooth coating that covers the surface of the bones inside the knee. Articular cartilage also cushions and helps lubricate the joint surfaces (see the anatomy section for further information about articular cartilage). In osteoarthritis the articular cartilage begins to degrade. Over time the articular cartilage can thin or form cracks. Pieces of cartilage may come loose and float inside the knee, further irritating the joint. After a long period of time the cartilage can become completely “worn away” and the bones begin to rub together.
Osteoarthritis usually comes on slowly and results in knee pain, stiffness and/or swelling. Sometimes a grating sound can be heard when the knee is bent – such as when climbing up and down stairs or crouching. Bumps or nodes may appear around the knee joint. Sometimes a knee can have a mild amount of osteoarthritis and feel perfectly fine.
Most types of treatment for osteoarthritis of the knee work best when started early, before there is a lot of “wear and tear” in the knee. For this reason establishing a correct diagnosis is very important. In some cases osteoarthritis of the knee can be diagnosed based on the medical history and physical examination of the affected joint(s). An x-ray may be ordered to determine how much joint damage there is. Sometimes blood tests or joint fluid tests are ordered to confirm the diagnosis or to distinguish between different types of arthritis.
No one knows for sure what causes osteoarthritis but some risk factors include:
- Previous knee injury i.e. meniscal tear, ligament injury.
- Family history of osteoarthritis.
- Being overweight.
- Damage to the knee from another type of arthritis.
- Increasing age.
A lot can be done to help people who have osteoarthritis in their knee(s). The goal of treatment is to reduce pain, control swelling and maintain or improve mobility of the knee but unfortunately there is no known cure for osteoarthritis.
Every osteoarthritic knee is different, and there should be a team approach to treatment. Some available treatments include exercises, medications, education on activity modification, weight loss, heat and cold therapy, techniques for joint protection, injections and in some cases surgery. Doctors and physical therapists who deal with people who have osteoarthritis can help outline a treatment program.
There are two main types of oral medications which have been shown to relieve pain and the other symptoms of osteoarthritis of the knee: acetaminophen (Tylenol) and non steroidal anti-inflammatory drugs (NSAIDs).
Narcotic drugs (eg. codeine, morphine, percocet) are rarely used when pain is not controlled by the above mentioned medications alone. However, they do carry unfortunate side effects of nausea, vomiting, dizziness, and constipation and are therefore prescribed for short term use only. Prolonged used of these drugs for pain management of osteoarthritis is not recommended. Often they are used as a last resort while patients await surgery. Consultation with a physician is important before starting any regular oral medications.
Injections are given by a needle directly into the knee joint. There are two types of injections used to treat symptoms of knee osteoarthritis: joint lubricants (viscosupplementation) and cortisone (steroid injection).
Articular cartilage is the smooth coating covering the surface of the bones inside the knee. It helps to lubricate and cushion the surfaces of the knee joint. In osteoarthritis, this coating is damaged leading to reduced lubrication and cushioning. This results in some of the pain, grinding, and other symptoms experienced by osteoarthritis-sufferers (see the osteoarthritis section for further information).
Viscosupplementation therapy involves injecting a clear gel-like substance directly into the knee joint. These injections help to restore some of the lubrication lost by damaged cartilage and thus improve symptoms. An injection is given as one shot into the knee joint each week for three weeks. Usually people who respond to this form of treatment will experience some improvement for six to ten months. An injection series can be repeated every six months as needed. This method of therapy is used for people who have not benefited from less invasive therapies such as lifestyle modification, physiotherapy, and oral medications. The injections do carry a small risk of infection or allergic reaction to the lubricant itself mon brands include Synvisc© and Orthovisc Euflexxa©. Physicians and orthopedic surgeons can provide additional information about the risks and benefits of this procedure.
Physicians can inject a powerful anti-inflammatory drug called cortisone (or corticosteroid) directly into the joint. Cortisone injections are reserved for people with a severely inflamed knee with uncontrolled pain. Cortisone injection can provide rapid relief from a tender, swollen osteoarthritic knee which has failed to respond to other forms of treatment. The benefit of an injection may last anywhere from a few days to more than 6 months. Injections may be less effective with each successive injection.
It should be noted that although cortisone is a steroid, it differs from the performance enhancing steroids used by some athletes and discussed in the media. Injectable cortisone does not have the side effects associated with such steroids. There are however some risks associated with cortisone injection. Repeated injections may promote the breakdown of articular cartilage, which is the cause of osteoarthritis in the first place. For this reason, multiple injections are not usually recommended. There is also a small risk of infection or allergic reaction to the steroid preparation. Some patients may experience a “steroid flare” in which the joint becomes more inflamed for 2-3 days following injection. Anti-inflammatory medications and/or ice may prevent or control this reaction. Doctors should explain all the risks and side effects prior to giving any steroid injection.
To read more about osteoarthritis of the knee please visit the links section. Links have been provided to other websites as well as online medical journals. Knee injury topics can also be accessed.