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Knee Pain

  • Knee pain has many causes, including pathologic processes in the knee and disorders in distant locations with referral to the knee area.
  • Diffuse or located in a specific region
  • A characteristic history and physical examination frequently narrow the diagnosis.
  • Classification:
    • Traumatic
    • Acquired
Risk Factors
  • Athletic activity
  • Obesity
  • Sedentary lifestyle
  • Traumatic injury
  • Overuse injury
  • Disease process(es) in or around the knee
Associated Conditions
  • Rheumatoid arthritis
  • Active lifestyle
Signs and Symptoms
  • General:
    • Swelling
    • Locking
    • Popping
    • Difficulty with stairs and rising from a chair
    • Chronic pain with increased activity
  • Patellofemoral conditions:
    • Patellofemoral syndrome:
      • Typically occurs in young adults
      • Involves articular cartilage softening
      • Pain is most frequent in the anterior knee and is worse with stairs.
      • Knee ROM often has a grating sensation, and pain is elicited by pressing firmly on the patella.
    • Patellar subluxation dislocation:
      • Traumatic
      • Can be related to a combination of structural variations (compared with normal anatomy) in the knee and leg: Femoral anteversion and valgus (a configuration that increases the Q angle) and a laterally moving patella with an extended knee (J sign)
    • Articular cartilage injury:
      • Frequently related to a traumatic event
      • Pain is worse with activity.
  • Meniscal injuries:
    • Can be degenerative (with an incidental initial event) or traumatic (with a clear injury)
    • Swelling develops slowly and is activity related.
    • Locking or giving-way of the knee, along with medial or lateral joint line pain, is common.
  • Arthritis:
    • Symptoms frequently are gradual in onset and progressive.
    • Pain is worse with increased activity and improves with rest.
    • Pain at night after an active day is common.
  • Ligament tears:
    • ACL:
      • Prevents anterior translation of the tibia on the femur
      • Injured predominantly from noncontact decelerations such as stopping suddenly, pivoting, or landing after jumping
    • PCL:
      • Primary stabilizer to posterior translation of the tibia on the femur
      • Direct trauma to anterior knee (dashboard injury)
      • Knee pain and swelling occur after the injury, with improvement in generalized pain symptoms at several weeks.
      • Develop medial compartment and patellofemoral symptoms over time
    • MCL:
      • The primary restraint to valgus stress on the knee
      • Pain is felt along the medial aspect of the knee, typically extending proximally and distally along the region of the MCL.
      • Isolated MCL injuries occur from a direct blow to the lateral knee.
      • Can be associated with ACL and meniscal tears.
    • LCL:
      • Extends from the lateral femoral condyle to the fibular head
      • Isolated injury to the LCL is rare.
      • LCL Injury frequently is associated with a cruciate ligament injury.
      • Assessment of the peroneal nerve is important.
  • Quadriceps or patellar tendon rupture:
    • Causes a loss of extension of the leg
    • Symptoms include the inability to extend the knee actively, pain, and knee effusion.
    • Often a palpable defect and a patella that appears more distal (quadriceps) or more proximal (patellar) than normal
    • Most frequent cause is direct trauma to the knee or forced flexion of the knee that is resisted by maximal quadriceps contraction.
  • Bursitis and tendinitis:
    • Inflammatory changes occur in the bursa or tendon insertions around the knee, typically with tenderness to direct palpation over the anatomic location.
  • Osteochondritis dissecans:
    • Observed in children and young adults who are active and participate in sports
    • Result of localized bone necrosis with loss of overlying cartilage support
    • Symptoms include knee pain, effusion, tenderness over the lesion, and (occasionally) locking or catching of the knee if the fragment has become a loose body in the joint.
    • Pain often is insidious and related to activity.
  • OSD:
    • An overuse syndrome from repetitive stress on the tubercle, resulting in an apophysitis of the patellar tendon insertion
  • Baker cyst (popliteal cyst):
    • Caused by a distended capsule in the posterior fossa of the knee, often directly connected to the joint space
    • Most often associated with intra-articular disease
    • Presents as a mass in the popliteal fossa of the knee
    • The intra-articular disorder may not be symptomatic; therefore, the patient may complain only of posterior knee fullness.
  • Fracture:
    • Fracture about the knee should be ruled out in any patient with a traumatic injury.
    • Can occur in the distal femur, proximal tibia, and patella
    • Usually, plain AP and lateral radiographic views are sufficient.
  • Bone tumor:
    • Rare, but should be a differential diagnosis in patients with night pain
    • Most patients have musculoskeletal pain.
      • Typically described as dull, deep, aching
      • Often becomes constant
      • Many patients experience pain at night.
      • May not be related to activity
    • Patients also may complain of swelling, loss of function at the involved site, weight loss, or acute symptoms of a pathologic fracture.
Physical Exam
  • Palpate the joint for:
    • Effusion and localized swelling
    • Joint line tenderness (Medial and lateral tenderness suggests meniscal tear or arthritis.)
  • Compare ROM of the affected knee with that of the contralateral knee.
  • Observe patellar tracking as the knee is ranged from flexion to extension.
  • Check joint stability (MCL, LCL, ACL, OSD).
  • Order serum laboratory tests based on a suspicion for specific clinical entities, as follows:
    • Septic arthritis: Complete blood count with differential ESR, C-reactive protein
    • Rheumatoid arthritis or other inflammatory arthritis: Rheumatoid screen, including rheumatoid factor and antinuclear antibody
    • Gout: Serum uric acid level
  • The 1st step is plain radiographs (including weightbearing posteroanterior, lateral, and tangential [Merchant] views) of the patella.
  • MRI is used to detect meniscal tears, ligament injury, synovial proliferative disorders, tumors, and AVN.
Diagnostic Procedures/Surgery
  • Arthrocentesis often can aid in establishing a definitive diagnosis.
    • With septic arthritis, findings include positive culture and elevated white blood cell count (>50,000).
    • With gout, findings include uric acid crystals.
    • Fat droplets suggest intra-articular fracture.
Pathological Findings
Depend on causative factors
Differential Diagnosis
  • A complete differential diagnosis is beyond the scope of this chapter, but most common:
    • Patellofemoral conditions
    • Articular cartilage injury
    • Meniscal disorders
    • Arthritis
    • Ligament tears
    • Tendinitis and tendon ruptures
    • Osteochondritis dissecans
    • OSD
    • Baker cyst
    • Gout
    • Fracture
    • Tumor
  • The diagnosis can be made by symptoms and history in conjunction with the physical examination and imaging studies.
General Measures
  • Patellofemoral syndrome: Anti-inflammatory medication and exercise
  • Patellar subluxation-dislocation: Often improved by extensive physical therapy and patellar bracing
  • Arthritis: Initially, analgesics, activity modification, injections, unloader bracing
  • Bursitis and tendinitis: Analgesics, topical treatments, activity modification
  • OSD: Rest and activity modification
  • Ligamentous and meniscal injuries: Protected ROM and weightbearing, ice, analgesics, and orthopaedic referral
Special Therapy
Physical Therapy
  • Excellent for treating patients with knee pain
  • Therapists:
    • Concentrate on ROM; quadriceps, hamstring, and core strengthening; and stretching.
    • May include modalities such as cryotherapy, electrical stimulation, and ultrasound
  • NSAIDs
  • Acetaminophen
  • Mild narcotic analgesics
  • Intra-articular hyalurans
  • 3 main categories of knee surgery:
    • Arthritis: Arthroscopic meniscal and cartilage debridement, tibial and femoral osteotomy, total and hemi knee replacement
    • Sports medicine: Arthroscopic evaluation and treatment of meniscal and ligament injuries, patellar mechanism realignment
    • Trauma: Internal fracture fixation, tendon rupture repair
Excellent with well-defined diagnoses and appropriate surgical and nonsurgical treatment
  • Loss of motion
  • Loss of function, particularly weightbearing
  • Chronic pain
Patient Monitoring
Patients are followed at 4-6-week intervals until they regain strength and ROM.
  • 719.46 Pain in joint
  • 719.6 Knee pain
Patient Teaching
Depends on causative pain factors
Q: What is a sensitive physical finding for intra-articular knee pathology?
A: In addition to localized tenderness, a knee effusion suggests intra-articular abnormality.
Q: How do meniscal tears occur?
A: Meniscal tears can occur with an acute ligament injury, such as an ACL injury, or in chronically ligament-deficient knees because the menisci serve as secondary knee joint stabilizers. Degenerative tears can occur in the meniscus from malalignment, overuse, and repetitive trauma.

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