• Information
  1. Differential Diagnosis of Knee Pain
  2. General Examination
  3. Additional Knee Examinations
  4. Ligamentous Injuries
  5. Popliteal Cysts
  6. Anserine Bursitis
  7. Prepatellar Bursitis
  8. Patellofemoral Pain Syndrome

A. Differential Diagnosis of Knee Pain [3]

1. Osteoarthritis (OA)
   1. Should be considered in any older person, particularly if overweight
   2. Age >50, morning stiffness <30 minutes, crepitus, or bony enlargement common
   3. Sensitivity of these 89%, specificity 88%, for exacerbation of underlying chronic OA
2. Inflammatory Chronic Arthritis
   1. Rheumatoid arthritis, spondyloarthritis, others
   2. Prominent morning stiffness; other joints affected
   3. Synovial fluid leukocytosis, increased ESR or CRP
3. Gout or Pseudogout
   1. Other joints affected, swollen and tender
   2. Synovial fluid with crystals and usually leukocytes
4. Hip Arthritis
   1. Pain with hip rotation
   2. Groin tenderness
5. Chondromalacia Patellae
   1. Relatively young patients
   2. Predominantly patellofemoral symptoms
   3. Tenderness over patellofemoral joint
6. Anserine Bursitis - tenderness distal to knee, over medial tibia
7. Trochanteric Bursitis
   1. Lateral hip pain
   2. Tenderness (point) over lateral hip
8. Joint Tumors
   1. Nocturnal and/or continuous pain
   2. Bloody synovial fluid
   3. Abnormal radiograph possible (CT or MRI scan preferred)
9. Meniscal or Ligmaent Tear - see below

B. General Examination [1]

1. Physical Examination
   1. Cannot reliably detect all fractures without plain radiographs
   2. Moderately sensitive and fairly specific for meniscal or ligamentous injury
   3. Sensitivity for meniscus 87%, anterior cruciate ligament 74%, posterior cruciate 81%
   4. Specificity for meniscus 92%, anterior cruciate ligament 95%, posterior cruciate 95%
   5. Magnetic resonance imaging (MRI) more sensitive, less specific for meniscus/ligament problems
   6. Exacerbation of osteoarthritis must be considered, particularly in persons >50 years
2. Appearance - comparison of two knees
   1. Color and heat
   2. Swelling, effusion
   3. Bulge sign - present with small effusions
   4. Blotting of patella - like floating; present with larger effusions
   5. Inspect for pre-patellar effusion
   6. Posterior (popliteal) effusion with bulge may be a Baker's Cyst
   7. Examination of muscles surrounding knee - especially for atrophy
   8. Valgus (knock knee) and varus (bow leg) deformities
3. Tenderness at Rest and with Motion
   1. Inflamed knee
   2. Pain below knee, medial portion of tibia may be Anserine Bursitis
   3. Range of Motion - passive and active
4. Flexion and Extension
   1. Extension to > -5° is hyperextension = genu recurvatum
   2. Failure to extend to <5° is evidence of a flexion contracture
   3. Full flexion is ~140°
5. Diagnostic accuracy of physical examination of knee is very low for ruling out meniscal tear and other abnormalities; history and radiographic testing are critical [4]

C. Additional Knee Examinations

1. Knee Radiographs [1]
   1. Decision to obtain knee radiographs to rule out fracture best by using Ottawa knee rules
   2. Negative result on Ottawa knee rule test excludes knee fractures after acute injury [5]
   3. Radiographs should be obtained per Ottawa rules for any of the following:
   4. Injury due to trauma and age >55 years
   5. Tenderness at head of fibula or patella
   6. Inability to bear weight for 4 steps
   7. Inability to flex the knee to 90°
2. Knee Aspiration [2]
   1. Simplest joint to aspirate. Note that the patella is slightly dome shaped
   2. Patient should have leg as extended as possible
   3. The medial and/or lateral pataller ridge is palpated and an "X" marked in center or ridge
   4. The area is sterilized with 4-6 wipes of antiseptic such as betadyne®
   5. A small (1-2cc of 1%) amount of lidocaine is injected subcutaneously then deeper
   6. Initially, a 25ga or smaller needle is used
   7. Then a 22ga 1.5" needle can be used; this should be sufficient to enter the joint
   8. The needle is advanced horizontally then the head is pointed slightly up (patella dome)
   9. Gentle suction is maintained on the needle during advancement
   10. A 20ga or 18ga needle may be required if joint fluid is very thick
   11. Large effusions may re-accumulate and require repeat aspiration
   12. Normal joint fluid is clear, sticky, and viscous with a slight yellow tint
3. Contraindications to Knee Aspiration [2]
   1. Bacteremia
   2. Inaccessible joints / joint prosthesis
   3. Overlying infection of soft tissue
4. Injections of Lidocaine and Glucocorticoids [2]
   1. These are guidelines; smaller joints receive less of each agent
   2. Typically, ~0.5-3cc of 1-2% lidocaine is injected first at the most tender point(s)
   3. If this relieves pain, then ~10-80mg of DepoMedrol® can be injected into the area
   4. Care is taken not to inject the tendons
   5. If a needle is in the tendons, then injection will be resisted (withdraw needle)
   6. Injection of glucocorticoids into knees every 3 months did not accelerate cartilage loss [6]
5. Failed Knee Aspiration
   1. Usually explicable in anatomic terms
   2. High Fluid viscosity - leads to blockage in needle; common in rheumatoid arthritis
   3. Lipoma arborescens - fatty villous hypertrophy due to chronic effusions
   4. Obesity - common misdiagnosis of effusion; difficult to find landmarks
   5. Lateral approach more likely to yield fluid

D. Ligamentous Injuries

1. Anterior (ACL) and Posterior Cruciate (PCL) Ligaments
2. Lateral and Medial Collateral Ligaments
3. Injury to the Medial Meniscus
   1. Medial knee tenderness with rupture
   2. Injury occurs when knee twisted medially while flexed and weight bearing
   3. Bucket handle tear (most common): horns remain attached while curved portion is torn
   4. Less common: Cartilage may be split longitudinally OR
   5. Either anterior or posterior horn may be torn
4. injury to the Lateral Meniscus
   1. Lateral knee tenderness with rupture
   2. Pain in knee joint on lateral OR paradoxically medial side
   3. McMurray and Apley's tests may be positive
5. Examination of Ligaments
   1. Patient should indicate site of pain and antecedent trauma
   2. Patient should indicate specific motions that cause locking (normal locking at 170°)
   3. General examination as above
   4. McMurray Test: sensitivity 52%, specificity 97% for mensical tears
   5. Apley Test
6. McMurray Test
   1. Patient supine on table
   2. Grasp knee with one hand so fingers press medial and lateral aspects of joint
   3. Grasp heel with other hand so plantar surface of foot rests along wrist and forearm
   4. First, flex knee until heel nearly touches the buttock
   5. Next, rotate foot laterally to test posterior half of medial meniscus
   6. With foot in continual lateral rotation, bring leg up so knee makes right angle
   7. Medial meniscal tear is present if click is felt or heard during extending motion AND patient recognizes it as the sensation preceding pain or locking
7. Apley Test
   1. Patient lies prone on a low crouch, about 2 feet high
   2. Affected limb towards exmination side
   3. Grasp foot with both hands and flex knee to 90°
   4. Rotate the foot laterally, which should cause little discomfort
   5. Next, rest examiners knee on patient's hamstrings to fix the femur
   6. Pull leg to further flexion while foot is held in lateral rotation
   7. Pain on this further flexion indicates a lesion of tibial collateral ligmaent
   8. Then compress teh tibial condyles onto femoral condyles by forcing examiner's body weight onto the plantar surface of foot, still in lateral rotation
   9. Pain from this maneuver indicates tear of medial meniscus

E. Popliteal Cysts

1. Also called Baker's Cysts
2. Dissection or rupture can cause symptoms very similar to venous thrombosis
3. Best seen with patient standing, observed from behind
4. About 40% of population have knee joint-bursa communication
5. Most common with rheumatoid (RA) and osteoarthritis (OA), or knee injuries
6. Ultrasound or MRI usually used to document the presence of a cyst
7. Treatment
   1. Inflammatory Etiology - usually with RA; good response to glucocorticoid injection
   2. Due to Osteoarthritis or injury - best treated with surgery to correct injury

F. Anserine Bursitis

1. Most commonly in overweight patients with Osteoarthritis of the knees
2. Pain and tenderness over medial aspect of the knee, ~5cm below joint margin
3. Pain worse on exertion, especially climbing stairs
4. Pain on palpation, especially on flexion
5. Lidocaine given locally should alleviate pain; if so, glucocorticoid injection is given

G. Prepatellar Bursitis

1. Usually caused by trauma to knee, often from frequent kneeling
2. Previously called "housemaid's knee."
3. Lies anterior to lower half of patella
4. Infrapatellar bursa (between patellar ligament and tibia) may be involved
5. May become infected so that aspiration of the bursal fluid can be critical
6. If no infection is demonstrated, then glucocorticoid injection can be helpful

H. Patellofemoral Pain Syndrome

1. Pain and crepitus (on motion) in the patellar region
2. Pain occurs when patella is compressed against the femoral condyle or displaced laterally
3. Joint effusions uncommon; small if they do exist
4. Pain worse on stair climbing, other acitivities
5. However, there is an inflammatory component with stiffness in knee after inactivity
6. Predisposing conditions include patella alta, abnormal quadraceps angle, and trauma
7. Treatments
   1. Acetaminophen and NSAIDs
   2. Ice and rest
   3. Avoid overuse
   4. Quadraceps strengthening
   5. Consideration for surgical correction (realignment)

References

1. Jackson JL, O'Malley PG, Kroenke K. 2003. Ann Intern Med. 139(7):575
2. Zuber TJ. 2002. Am Fam Phys. 66(8):1497
3. Felson DT. 2006. NEJM. 354(8):841
4. Scholten RJ, Eville WI, Opstelten W, et al. 2001. J Fam Pract. 50:938
5. Bachmann LM, Haberzeth S, Steurer J, ter Riet G. 2004. Ann Intern Med. 140(2):121
6. Raynauld JP, Buckland-Wright C, Ward R, et al. 2003. Arthritis Rheum. 48(2):370