Osteoarthritis of the hip and knee

Osteoarthritis (OA) of the hip (coxarthrosis) and knee (gonarthrosis) is a disabling joint disease characterized by degeneration of the joint complex (articular cartilage, subchondral bone, and synovium). Although the exact etiology is unknown, risk factors include advanced age, joint overuse, obesity, previous injuries, and asymmetrically stressed joints (as in hip dysplasia, Perthes disease, etc.). Patients in the early phase of the disease present with joint stiffness and pain on initial movement and on constant, severe load bearing. During the later stages of the disease, excruciating pain may appear even during rest. Additionally, range of motion is drastically reduced and discrepancies in limb length, alignment, or stability appear. Diagnosis is predominantly based on clinical and radiological findings. Initial treatment includes lifestyle changes and physical measures (joint braces, occupational therapy, weight loss), and pain medication (NSAIDs). If medical interventions fail to improve the patient's quality of life, surgical procedures such as joint replacement may become necessary.

For more general information on osteoarthritis, see the respective article.

• The risk of developing hip and knee OA increases with age. The number of people affected by knee and hip OA in the USA is increasing because of a general increase in average life expectancy.
• Age: Peak incidence at initial diagnosis is 50–60 years of age.
• Sex: ♀ > ♂, especially in patients older than 50 years

Osteoarthritis is the most common disease of the hip joint in adults!

References:^[1][2][3]

Epidemiological data refers to the US, unless otherwise specified.

• See table under “Etiology” in osteoarthritis.
• Primary: idiopathic
• Secondary
  • Hip osteoarthritis due to Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, developmental dysplasia of the hip, hemochromatosis, gout, stiffened ipsilateral knee joint
  • Knee osteoarthritis due to genu valgum, genu varum, cruciate ligament rupture, meniscal tear

References:^[4]

See also "Clinical features” in osteoarthritis.

• Hip osteoarthritis
  • Pain in the groin area and above the greater trochanter
  • Increased contracture in the flexor, external rotation, and adduction position → antalgic gait
  • Early signs: limited and painful internal rotation of the hip joint
  • Pain on palpation: greater trochanter, groin
  • Positive Thomas test
    • Function: test for hip flexion contracture
    • Position: supine
    • Procedure: Examiner passively flexes the hip joint opposite to the affected side to a maximum to compensate lumbar lordosis.
    • Positive test: If flexion contracture is present, the ipsilateral leg will simultaneously flex independently as a reflex.
• Knee osteoarthritis
  • Function-limiting knee pain
  • Knee swelling which increases on activity
  • Mechanical instability, locking, catching sensation
  • In case of patello-femoral osteoarthritis: positive Patellar grind test (pain on movement of the patella)
  • Cartilage damage usually begins medially and may lead to genu varum (bowing of legs)

Walking downhill is painful with knee osteoarthritis, whereas walking uphill is painful with hip osteoarthritis!References:^[5][6]

Conventional x-ray

• General: radiological signs of osteoarthritis
• Indirect evidence of knee osteoarthritis through uneven pressure distribution
  • Patella lateralization
  • Genu valgum, genu varum

Conservative

• Frequent exercise, minimal load → Joint-friendly exercises are also recommended after endoprosthesis implantation (swimming and cycling).
• Weight loss may be indicated.
• Physical therapy
• Pain medication (WHO pain ladder)
• Use of a forearm-supported crutch on the healthy, unaffected side when walking
• Orthotic insoles

Surgery

Indications for surgery are primarily based on the level of patient suffering.

Hip replacement

• Total hip replacement
  • Description: total hip joint replacement with replacement of the femoral head and the acetabulum with a prosthesis
  • Indications
    • Primary arthritis with total joint destruction; and exhausted conservative measures
    • Femoral neck fracture with concomitant hip osteoarthritis
• Hip hemiarthroplasty
  • Description: only femoral prosthesis is implanted, with preservation of the native acetabulum
  • Types:
    • Fixed head prosthesis (unipolar head prosthesis): consists of a single, undivided, femoral component with a fixed head, of a diameter that matches that of the acetabulum; the head component articulates directly with the acetabular articular cartilage.
    • Dual-head prosthesis (bipolar head prosthesis): has a femoral head that swivels during movement; this additional articulation in the prosthesis helps reduce the amount of wear and tear on the new joint for longer-lasting results.
  • Indications
    • Femoral neck fractures in older patients without concomitant hip osteoarthritis
    • Primary arthritis with complete joint destruction in older patients
• Postoperative deep venous thrombosis prophylaxis is needed for hip replacement and any surgery to correct a fracture close to the hip joint.
  • Perioperative start
  • For 28– 35 days postoperatively

Knee joint replacement

• Nonconstrained prosthesis
  • Unicondylar knee replacement
    • Description: unicompartmental prosthesis of the femoral and tibial articular surface with insertion of a plastic sliding surface (mainly polyethylene) between both prosthetic components
    • Indication: unilateral osteoarthritis of the inner and outer surface of the joint; more frequently internal in varus gonarthrosis
  • Bicondylar knee replacement(total knee replacement)
    • Description
      • Both condyles of the femur and the joint surface of the articular surface of the tibial head are replaced.
      • Insertion of a plastic sliding surface (mainly polyethylene) between both prosthetic components
      • If necessary, additional replacement of the posterior surface of the patella (tricondylar knee replacement)
    • Indication: knee osteoarthritis, which is nonresponsive to conservative treatment and severely restricts the patient's quality of life
  • Patellofemoral joint replacement
    • Description: prosthetic replacement of the femoral trochlear (= patella condyle) and the rear surface of the patella
    • Indication: mainly isolated degenerative alterations of the femoropatellar joint
• Constrained prosthesis: rotating hinge knee prosthesis
  • Indication: severe knee osteoarthritis with ligament insufficiency and femorotibial rotational malalignment
  • Description: analogous to the bicondylar knee prosthesis; However, the femoral and tibial components are larger shaft prostheses that are more deeply anchored and are connected via a movable axis.
• Postoperative deep venous thrombosis prophylaxis: should be administered for knee replacement and any surgery to correct a fracture located close to the knee joint
  • Perioperative start
  • For 11–14 days postoperatively

Other surgical procedures

• Corrective osteotomy (valgus or varus)
  • Indication
    • E.g., unilateral osteoarthritis of the knee
    • Young patients with correctable joint malformations
• Arthrodesis: surgical fusion of the joint; very rare in osteoarthritis of the hip and knee

References:^{[7][8][9][10]}

Complications after osteosynthesis/arthroplasty

• Infection
• Injury to surrounding structures (tendons, nerves, vessels)
• Thrombosis, embolism
• Hemorrhage
• Material fracture, bone fracture
• Post-traumatic osteoarthritis
• Malalignment/dysfunction
• Compartment syndrome
• Nonunion

Special complications: soft tissue ossification/myositis ossificans (heterotopic ossification)

Soft tissue and muscle ossification (heterotopic ossification) can occur congenitally or after tissue or joint injuries or surgery.

Localized course (myositis ossificans localisata)

• Etiology
  • Post-traumatic: especially after implantation of an artificial hip joint and after polytrauma
  • Neurogenic: after nerve injuries, meningitis, and spinal cord injuries
  • Chronic degenerative disease (e.g., in ankylosing spondylitis)
  • Muscle overuse (e.g., in athletes)
• Clinical features: restriction of movement, muscle stiffness
• Diagnostics
  • Soft tissue ossifications are detectable in conventional x-ray.
  • Radiological findings: periarticular soft tissue calcifications
  • Laboratory findings: ↑ alkaline phosphatase
  • Positive scintigraphy
• Treatment: radiotherapy, possibly surgery
• Prophylactic measures against recurrence
  • Single dose radiotherapy recommended (possibly postoperative or preoperative)
  • Alternative: postoperative administration of NSAID (indomethacin)

Progressive generalized disease (myositis ossificans progressiva/fibrodysplasia ossificans progressiva)

• Etiology: extremely rare, autosomal dominant hereditary disease
• Pathophysiology: Fibrocytes produce bone tissue instead of scar tissue in all types of trauma.
• Clinical features
  • Generalized ossification mainly from cranial to caudal (life-threatening if the respiratory muscles are affected)
  • Malformation of toes is frequently observed at birth.
  • During the course of the disease, large, painful, well-vascularized swellings appear at various sites, which develop into bone tissue after regression.
• Treatment
  • No causal treatment
  • Symptomatic: NSAIDs, radiotherapy, possible surgical removal of individual lesions

References:^[11][12]

We list the most important complications. The selection is not exhaustive.