We demonstrate some simple technques a professional therapist may use to diagnose knee pain.
In order to properly assess the knee joint a good knowledge of its anatomy is needed. See the knee anatomy page for further details. Within the knee joint lie numerous structures that are prone to injury, some more so than others. Hence a systematic and thorough examination is needed to ascertain which structures have been damaged.
Below is an outline of a knee assessment which may be used in diagnosing knee pain, following an injury. This is for information purposes only and should only be conducted by those qualified to do so.
When considering any knee injury the first and most important step is to take an accurate history. In alot of knee injuries a working diagnosis can be formed just from the patients account of the event alone. Here are a number of aspects that should be elicited from the initial discussion with the patient.
- Mechanism of injury-The most important question to ask is how thise injury was caused i.e. what was the athlete doing on the onset of pain and what were their symptoms immediately afterwards. Twisting injuries and subsequent symptoms of the knee "giving way" are commonly associated with ACL injuries. Locking of knee is common to meniscal injuries.
- Demonstration of the mechanism of injury- get the patient to act out how they injured their knee, on their affected side if possible.
- Audible sounds- Was there any added sounds heard at the time of the injur? A "pop" or a "snap" are sometimes heard on rupture of the ACL. A clicking noise on movement can indicate a meniscal injury.
- Pain location- Localized pain at the medial or lateral boarders of the knee can indicate MCL or LCL injuries.
- Severity of Pain- this is not always an accurate marker as an ACL rupture is known to less pain painful than a milder ligament sprain.
- Swelling- If bleeding occurs into the knee joint (joint hemarthorsis) in the first few hours the knee visibly swells- this is a common symptom of ACL, PCL, tibial plateaux fractures and torn meniscus injuries.
Objective (Physical) Examination:
As well as taking an accurate history, it is important to carry-out a comprehensive physical assessment. This involves testing every structure in the knee- even if you have a good idea what the injury is. Depending on the mode of injury, it is not uncommon for more than one structure to be damaged.
- Observe the patient in standing, walking and lying. Note ability to weight bear during mobilization and amount of swelling present in the knee. Listen for audible cracks or clicks.
2. Active Movements:
- Ask the patient to actively move the injured knee through flexion and extension. Compare range of motion to the uninjured knee and note any added pain on movement.
- Ask the patient to perform a straight leg raise in lying. This gives a good indication of muscle strength.
3. Passive Movements:
- The patient relaxes the muscles in the injured leg allowing the therapist to passively flex and extend the knee through the available range.
- Watch for signs of "muscle guarding" (muscle contraction brought on by pain to prevent further movement of the limb), audible clicks and quality of movement e.g. stiffness or a soft "end-feel" at the end of range.
- Only after seeing the available movement in the knee should the area be palpated. The following sites should be palpated:
- The joint lines both medial and lateral sides- pain may indicate an MCL or LCL injury
- Patellofemoral joint- patellar tendon and quadriceps tendon
- Patella- move the patella in all directions
- Posterior joint- look for signs of Bakers cyst and palpate the muscle tendons of the gastrocnemius and hamstrings.
5. Special Tests:
A number of special tests exist to investigate the individual structures of the knee. These include
A. Ligament Stability Tests:
- Anterior cruciate ligament - Lachmans and anterior drawer.
- Posterior cruciate ligament - stressing the ligament.
- LCL- pressure on medial aspect of knee when in 30 degrees
- Medial ligament - pressure on lateral side of knee joint when in 30 degrees of flexion.
B. Meniscal Tests:
- Medial Meniscus- McMurrays.
- Lateral Meniscus- McMurrays.
- Rotating and pressing down on the knee in prone position.
- Assess the 'tracking" movement of the patella both medial and laterally. This is particularly important in cases where a patellar dislocation has been suspected.
- Scoop test for swelling on the knee.
- Glide test for pain under the patella.