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EricT · 05-10-2006, 08:16 AM

From Jonathan Cluett, M.D.,

What is causing my knee pain?
Understanding what is causing your knee pain must be understood in the context of the pain. How old are you? Was there a traumatic event? Where is the pain located? Did the symptoms develop immediately or over time?

Once these questions are answered, you can begin to investigate the symptoms. Putting the symptoms together with the history often leads to a diagnosis.

Common Knee Symptoms

Popping
Popping and snapping within the knee is quite common, and often not a symptom of any particular problem. When the pops or snaps are painless, there is usually no problem--the bigger concern is when these sounds are associated with pain. A pop is often heard or felt when a ligament, such as the ACL, is torn.

Crunching/Grinding
A sense of grinding or crunching is most often associated with bone grinding against bone once the cartilage is worn away.

This is commonly found in arthritis. Patients who are young (under 50 years old) seldom have arthritis that will cause these severe symptoms, unless there has been a severe injury to the knee in the past.

Locking
Locking is a symptom that occurs when a patient cannot bend or straighten their knee. The locking can either be due to something actually blocking motion of the knee (this can occur when a piece of cartilage wedges within the joint) or when pain prevents the patient from moving the knee. These two causes must be differentiated, as something physically caught in the joint should be evaluated in a timely manner. Often injecting the knee with numbing medication can help determine the cause of locking.

Giving-Way/Instability
The stability of the knee is provided by the ligaments that connect the shin bone (tibia) to the thigh bone (femur). When the ligaments are stretched or torn, the knee may feel as though it is giving way beneath the patient. A sensation that the knee may give out from beneath you is a common symptom of ligament injury.

Swelling
Swelling of the knee is common with several different knee problems. When there is swelling immediately after an injury (within an hour), the most common causes are an injury to the anterior cruciate ligament or a fracture of the top of the shin bone. When swelling develops gradually over hours to days, the injury is more likely a tear of the meniscus or a ligament sprain. Swelling that occurs without the presence of a known injury can be due to arthritis (common), gout (less common), or a joint infection (uncommon).

Location of Pain
The location of the pain can be an important part of tracking down the symptoms.

Front of the knee: Pain over the front of the knee is most commonly related to the knee cap. Kneecap pain can be caused by several different problems.

Inside of the knee: Pain on the inside, or medial aspect, of the knee is commonly caused by medial meniscus tears, medial collateral ligament injuries, and arthritis of the joint.

Outside of the knee: Pain on the outside of the knee, or lateral aspect of the knee joint, is commonly caused by lateral meniscus tears, lateral collateral ligament injuries, IT band tendonitis, and arthritis of the joint.

Pain in the back of the knee: Pain in the back of the knee can be due to the formation of a cyst, called a Baker's Cyst, in the back of the knee joint. Also common is for kneecap pain to be felt in the back of the knee.

Timing of Pain

Some common situations cause pain typical of certain conditions.

While going down stairs: Pain while walking down steps is very commonly associated with kneecap problems, such as chondromalacia.

Morning pain: Pain after first waking in the morning that resolves with gentle activity is typical of early arthritis. Often patients loosen the knee over the course of the day.

What tests can be performed to detect problems within the knee?
A skilled examiner can often detect the injury to the knee prior to ordering tests such as x-rays or MRIs. These tests and maneuvers are performed to detect specific problems within the knee joint. While any one test may not be diagnostic of a particular problem, by performing a good knee examination most common knee problems can be properly diagnosed.

Tests to Detect a Meniscus Tear

Joint Line Tenderness
Joint line tenderness is a very non-specific test for a meniscus tear. The area of the meniscus is felt, and a positive test is considered when there is pain over the area where the meniscus is found.

McMurray's Test
McMurray's test is performed with the patient lying flat (non-weight bearing) and the examiner bending the knee. A click is felt over the meniscus tear as the knee is brought from full flexion to 90 degrees of flexion.

Ege's Test
Ege's test is a specific maneuver to detect a meniscus tear. With a patient squatting, an audible and palpable click is heard/felt over the are of the meniscus tear. The patient's feet are turned outwards to detect a medial meniscus tear, and turned inwards to detect a lateral meniscus tear.

Tests to Detect Ligament Injury

Lachman Test
The Lachman test is the best test to diagnose an ACL tear. With the patient lying flat and relaxed, the examiner bend the knee slightly, about 20 degrees. The examiner then stabilizes the thigh while pulling the shin forward. Both the amount of translation (shifting) as well as the feel of the endpoint offer information about the ACL.

Anterior Drawer Test
The anterior drawer test is also performed with the patient lying flat. The knee is bent 90 degrees and the shin is pulled forward to check the stability of the ACL. An intact ACL will only allow the shin to come forward slightly. A torn ACL will allow the shin to move further forward.

Pivot Shift Test
The pivot shift test is a difficult maneuver to perform on a patient who is not under anesthesia. This test places a stress on the knee joint that forces a subluxation (partial dislocation) in patients who do not have an ACL. This test recreates the type of instability that caused the ACL injury.

Posterior Drawer Test
The posterior drawer is performed similarly to the anterior drawer test. This test detects injury to the PCL. By pushing the shin backward, the integrity of the PCL is tested. Excessive movement of the shin backwards is a sign of PCL injury.

Varus and Valgus Instability
Varus and valgus instability tests check the LCL and MCL, respectively. With the patient lying flat, and the knee held at about 30 degrees of flexion, the shin is shifted to each side. Insufficiency of the LCL or MCL will allow the knee to "open up" excessively. The test is repeated with the leg straight. If the knee still opens up excessively, then more than just the LCL or MCL was torn.

Dial Test
The dial test checks the rotation allowed at the knee joint. Patients who have posterolateral rotatory instability, may have excessive rotation at the knee joint. The test is done with the patient lying face down, and the knees bent about 30 degrees. The feet are turned outwards and compared to each other. Excessive rotation is a sign of posterolateral corner injury.

Tests to Detect Kneecap Problems

Patellar Grind Test
Patellar grinding is a nonspecific test where the examiner feels for abnormal grinding sensations under the kneecap with movement of the joint. If pressure on the kneecap recreates the symptoms this may indicate the kneecap is the culprit.

Patellar Facet Tenderness
The examiner can slightly lift up the kneecap and place direct pressure on the undersurface of the kneecap. By doing so, the examiner is looking for sensitive regions of cartilage underneath the kneecap.

Patellar Apprehension Test
Patellar apprehension is a sign of an unstable kneecap. While the examiner places pressure on the kneecap, the patient may complain of the sensation that the kneecap is going to 'pop out' of its groove. This is a sign of kneecap instability.

Some common knee tests with explanations, pictures, and vids:

http://www.sportsdoc.umn.edu/Clinica...m/lachmans.htm