Patients often describe pain localized to specific regions of the knee. While this is not always helpful to identify the etiology of the pain, practitioners should be aware of regional knee pain problems.
- Pain underneath the patella.
- Pain across the patella tendon or quadriceps insertion.
- Swelling in the anterior aspect of the knee.
- Patella feels unstable.
Anterior knee pain is a common complaint with a variety of causes (Table 12–7). Several factors are responsible for normal patellofemoral mechanics. The quadriceps tendon guides tracking of the patella. Of the four muscles, the vastus medialis obliquus is the primary stabilizer of the patella against the lateral pull of the vastus lateralis. Other factors that can affect normal patellofemoral mechanics include the shape of the patella, the shape of the trochlea groove, the shape of the femoral condyles, the length of the patella tendon, the patellofemoral articulating cartilage as well as tension of the extensor mechanism. Disruption or abnormality in any facet of this complex joint can lead to dysfunction and subsequent pain.
Table 12–7. Causes of Anterior Knee Pain. |Favorite Table|Download (.pdf)
Table 12–7. Causes of Anterior Knee Pain.
|Patellofemoral pain syndrome (runner’s knee)|
- Pain underneath patella and along extensor mechanism
- Usually related to change in activity level
- Pain over the medial facet of patella
- Apprehension on examination
|Quadriceps tendinitis||Pain at the proximal pole of the patella|
|Patella tendinitis||Pain at the distal pole of the patella|
- Seen in adolescents
- Pain and swelling over tibial tubercle
|Anterior horn meniscus tear|
- Uncommon injury
- Can be present in runners or gymnasts
- Pain along the anterior joint line
- Pain underneath patella
- Difficulty with stairs, more with descents
- Patellofemoral crepitus
When eliciting a history from a patient with anterior knee pain, it is important to attempt to distinguish whether the pain is derived from the anterior structures of the knee, or whether it is referred from the tibial-femoral compartments. Acute onset of anterior knee pain, with or without trauma, can signify quadriceps tendon rupture (see acute injury section) and prepatellar bursitis. Mild trauma may also result in patellar dislocation in individuals with anatomic malalignment causing excess lateral traction on the patella. It is important to distinguish a true dislocation that required reduction by trained personnel from a sensation of “dislocation” experienced by the patient, because this represents a difference in instability and severity. The cause of subacute or chronic anterior knee pain can often be narrowed based on the age of the patient (Table 12–8). Patellofemoral pain syndrome is one of the most common causes of anterior knee pain in the younger patient, especially in women, whereas osteoarthritis of the patellofemoral compartment is the most common cause in the older patient. In either case, pain is typically worsened by activity that puts increase load and pressure on the patella, such as ascending and descending stairs, squatting, or even rising from a sitting position. With knee extension, patients sometimes describe a grinding sensation. Pain typically localizes around or under the patella. Patients may note a sensation of knee buckling or giving way, but as stated earlier, this is a nonspecific finding that seems to be largely related to pain rather than pathologic process.
Table 12–8. Prevalent Causes of Anterior Knee Pain by Age. |Favorite Table|Download (.pdf)
Table 12–8. Prevalent Causes of Anterior Knee Pain by Age.
|Skeletal immature||Osgood-Schlatter disease||Pain over tibial tubercle|
|16–40||Patellofemoral syndrome||Pain underneath patella|
- Pain over distal pole
- For rupture, difficulty with active leg extension, palpable defect between patella and tibial tubercle
|50–70||Quadriceps tendinitis and ruptures|
- Pain over proximal pole
- For ruptures, difficulty with active leg extension, palpable defect between patella and quadriceps tendon
- Start up pain
- Pain under patella
The examination starts with the evaluation of gait and the evaluation of limb alignment. Any valgus or varus deformity of the limb, internal or external rotation of the leg should be noted. Patients, especially young females, with valgus alignment of their lower limb, commonly complain of anterior knee pain due to a weak quadriceps muscle, lateral pull of the patella, and lateral facet tenderness. The presence or absence of flexion contractures, recurvatum or abnormal position of the feet should also be noted. Significant recurvatum can reflect generalized ligament laxity that is prone to patella instability. Pronated feet also can lead to valgus alignment, which can lead to lateral subluxation of the patella and anterior knee pain. The examiner should note the position of the patella, whether it is in alta (patella sits high in the patellar grove relative to the femur) or baja (sits low). Patella alta usually leads to increased patella instability as the patella engages into the trochlea groove at a higher knee flexion angle. Patella baja usually presents after tendon injury or knee surgery and can present with increased anterior knee pain due to increased stress of the patellofemoral joint.
The examination should also include slow active unassisted range of motion of the knee to assess patella tracking. The ‘J’ sign can be appreciated when the patella slides laterally at terminal extension of the knee. This indicates an excessive pull of the vastus lateralis muscle, an increase Q angle, patella alta, shallow trochlea groove, a deficient vastus medialis obliquus, or all of the above.
Through careful palpation, the examiner can identify the source of anterior knee pain (Table 12–7). Focal tenderness at the superior or inferior pole of the patella represents quadriceps and patella tendinitis. Patients who have acute patella dislocation have tenderness over the medial facet with associated bruising. The patella should then be compressed against the femoral groove to elicit patellar pain. Crepitus during range of motion or pain with ‘grinding’ of the patella on the trochlea groove indicates patellofemoral arthritis. Patellar mobility or glide should also be evaluated. Medial and lateral glide of the patella is performed at full extension and at 30 degrees of flexion. The amount of glide is being quantified using a quadrant system with respect to the widest portion of the patella. The first quadrant means that the patella can be subluxed over the femoral condyle by less than 25% of the widest width of the patella, second quadrant is when the patella can be subluxed between 25% and 50% of the patella width and so forth. It is important to repeat the test at 30 degrees of flexion because most patella dislocations do not occur at full extension. They usually occur at gentle flexion, around 20–30 degrees. The lateral displacement of the patella is also known as the ‘apprehension test.’ An increase in pain or apprehension on the part of the patient for fear of the patella dislocating is a positive finding. The apprehension test is the most specific test for patella dislocation or instability. A normal patella should not be displaced beyond the second quadrant in either direction.
The quadriceps, or Q, angle is also an important physical examination. The Q angle is formed by the line of pull of the quadriceps and the patella tendon as they intersect at the patella. Clinically, the angle is measured between a line drawn from the anterior-superior iliac spine to the patella and a line drawn from the patella and the tibial tubercle. Normal Q angle should be 8 to 10 degrees for males and less than 15 degrees for females. The Q angle should be measured at full extension and at 90 degrees of flexion. Any value greater than 10 degrees for males is considered abnormal. Increased Q angle is one of the risk factors for patellofemoral syndrome.
Most patellofemoral injuries are treated nonsurgically. Rarely, patients undergo patellofemoral realignment for chronic problems that are nonresponsive to nonsurgical measures. Most of these ailments can be treated with physical therapy focusing on quadriceps strengthening, core stability, and hip strengthening exercises.
Dixit S, DiFiori JP, Burton M, Mines B. Management of patellofemoral pain syndrome. Am Fam Physician.
- Pain over medial joint line.
- Difficulty squatting or twisting.
- Pain over anteromedial portion of the proximal tibia.
Several structures on the medial aspect of the knee can cause pain. Careful palpation allows the examiner to localize the source of the discomfort (Table 12–9). Medial meniscus tears have characteristic joint line pain. MCL tears have pain along the MCL ligament, which extends from the medial epicondyle and the pes anserine area. Pes anserine bursitis causes pain over the pes insertion, which is distal to the joint line over the anteromedial tibia. Bursitis of the pes anserine bursa is very common, particularly in patients with knee osteoarthritis. Localized tenderness of the bursa can be located between the anteromedial tibial metaphysis and the insertion of the sartorius, gracilis and semitendinosus tendons at the pes anserine. MCL ligament sprain, as discussed above, is common following trauma to the lateral aspect of the knee and is associated with valgus laxity. Medial compartment osteoarthritis, as well as tears in the medial horn of the meniscus can also cause medial knee pain.
Table 12–9. Causes of Medial Knee Pain. |Favorite Table|Download (.pdf)
Table 12–9. Causes of Medial Knee Pain.
|Medial meniscus||Medial joint line, often posterior|
|MCL||Pain along the course of the ligament from medial epicondyle to pes anserine|
|Medial compartment osteoarthritis|
- Medial joint line, but more specifically along the bony edges
- Varus alignment of the patient’s limb
|Pes anserine||Pain along the anteromedial tibia where the hamstring and sartorius muscles insert|
- Pain over the lateral joint line.
- Difficulty squatting or twisting.
- Pain over fibula head.
Lateral knee pain, a somewhat uncommon complaint, can be caused by damage to several local structures (Table 12–10). In athletes, particularly runners and cyclists, tendinitis of the iliotibial band can develop from friction to the tendon as it passes over the lateral femoral condyle. Compression of the tendon typically causes pain. Lateral compartment osteoarthritis is unusual but can cause lateral joint line tenderness, particularly in patients with valus deformity. Lateral meniscus tears, which are less common than tears medial meniscus, cause pain along the lateral joint line.
Table 12–10. Causes of Lateral Knee Pain. |Favorite Table|Download (.pdf)
Table 12–10. Causes of Lateral Knee Pain.
|Lateral meniscus||Lateral joint line, often posterior|
|LCL ligament sprain||Pain along the course of the ligament from lateral epicondyle to fibular head|
|Lateral compartment arthritis|
- Lateral joint line, but more specifically along the bony edges
- Valus alignment of the patient’s limb
|Iliotibial band syndrome|
- Pain along the Gerdy tubercle or along the iliotibial band near the lateral epicondyle
- Common with runners or patients who have recent changes in activity level
|Biceps femoris tendinitis||Tenderness along the posterior portion of the fibular head and the insertion of the biceps femoris tendon|
|Peroneal nerve entrapment||Tinel sign along the fibular neck, usually 2 cm distal to the proximal tip of the fibular head|
- Fullness over the back of the knee.
- Difficulty achieving full flexion.
While there are few weight-bearing structures in the posterior knee, there are a few causes of posterior knee pain (Table 12–11). The neurovascular bundle of the leg travels through the popliteal fossa, so vascular events can be manifested by posterior knee pain, including acute arterial thrombosis as well as deep venous thrombosis. Large synovial effusions can cause a Baker cyst to develop in the popliteal fossa. Patients typically complain of symptoms of a synovial effusion, including pain with range of motion and on ambulation, but they may also complain of posterior knee pain or fullness. Occasionally, Baker cysts rupture, resulting in extravasation of synovial fluid into the calf and mimicking a deep venous thrombosis. Finally, tendonitis of the hamstrings or referred pain from lumbar spine osteoarthritis can cause posterior knee pain.
Table 12–11. Causes of Posterior Knee Pain. |Favorite Table|Download (.pdf)
Table 12–11. Causes of Posterior Knee Pain.
|Popliteal cyst||Posterior joint level, can sometime feel a mass|
|Gastronemius tightness||Tenderness along the heads of the gastronemius muscle insertion the distal portion of the femur, above the joint line|
|Generalized osteoarthritis||Diffuse pain|
|Thrombosis||Common with pain and positive Homan sign (50% of the cases). Distal limb swelling. Occasional with palpable cords|