Soft Tissue Knee Injuries (Tendon and Bursae)

Soft Tissue Knee Injuries (Tendon and Bursae)

Bryan J. Whitfield

John J. Klimkiewicz


  • Position of knee flexion directly affects this ratio. At knee flexion angles < 45 degrees, this ratio is > 1, whereas at knee flexion angles > 45 degrees, this ratio is < 1 (16).

  • At > 45 degrees, the patellar tendon has a mechanical advantage and is less susceptible to injury through tensile failure, whereas at positions < 45 degrees, the quadriceps tendon has a mechanical advantage and is less vulnerable to injury.

  • Tendon strain in response to tensile load is up to three times greater at the insertion sites than at the tendon midsubstance. Additionally, collagen fiber stiffness is less at the insertion sites. These biomechanical properties contribute to tendon rupture commonly occurring at their insertion sites rather than at their midsubstance (50,51).

  • Failure usually occurs during rapid eccentric muscular contraction when markedly higher forces can be generated as compared to concentric muscular contraction (12).

  • This most often occurs with trauma causing forced extension of a flexed joint.

  • Several metabolic diseases or direct steroid injection can predispose to tendon rupture. These conditions include hyperparathyroidism, calcium pyrophosphate deposition disease (CPPD), diabetes mellitus, chronic renal disease, gout, systemic lupus erythematosus, and rheumatoid arthritis (11,50).

  • Fluoroquinolone antibiotics and isotretinoin treatment have been associated with pathologic tendon alteration and increased incidence of tendon rupture (47,49).


  • The patellar tendon receives its blood supply from the vessels within the infrapatellar fat pad and retinacular structures (2,45).

  • The origin and insertion of the patellar tendon are relatively avascular.

  • Ruptures of the patella tendon most typically occur in patients less than 40 years of age and are frequently associated with sporting activities including football, basketball, and soccer (33).

  • Ruptures are most common through the tendon-bone junction at the distal pole of the patella.

  • Histologic examination of rupture tendon often demonstrates an area of degeneration thought to predispose these patients to injury.

  • Previous surgeries, including total knee arthroplasty, anterior cruciate ligament (ACL) reconstruction using autograft patellar tendon, and tibial intramedullary nailing, have been associated with postoperative patellar tendon ruptures (4,6,24).

Clinical Presentation

  • At time of injury, a pop is often heard with an acute onset of pain and swelling. Patient is usually unable to actively extend knee or maintain it in an extended position against gravity. Chronic cases present with an extensor lag (33).

  • A palpable defect is commonly present just below the distal pole of the patella.

  • Concomitant ACL injuries are not uncommon and should be clinically ruled out.

  • Plain radiographs often demonstrate a patella alta in comparison to the opposite knee using the Insall-Salvati Index (> 1.2)(1).

  • An osseous fragment is present at times at the distal pole of the patella when an avulsion is part of the injury.

  • Magnetic resonance imaging (MRI) is useful in cases where partial injury is suspected.


  • The quadriceps tendon is a coalescence of tendinous portions of the rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis muscles.

  • The quadriceps tendon receives its vascular supply from an anastomotic network including the lateral circumflex femoral artery, descending geniculate artery, and medial/lateral geniculate arteries (40).

  • There is an avascular region of the deep part of the quadriceps tendon measuring 1.5 × 3.0 cm.

  • Ruptures of the quadriceps tendon most typically occur in patients over 40 years of age and are three times more frequent than patella tendon ruptures. Unilateral injuries are up to 20 times more frequent than bilateral injury (18).

  • The site of rupture usually occurs through a degenerative area within the tendon and seldom occurs in younger individuals. Systemic disease can lead to tendon degeneration and predispose to infrequent bilateral tendon ruptures (29).

Clinical Presentation

  • Pain is often present before rupture. At time of injury, a pop is often heard with an acute onset of pain and swelling.

  • In cases of partial injury or complete injuries that do not extend to include the retinacular tissue, the patient may be able to extend and resist gravity with an associated extensor lag, but in complete injuries, this is not possible.

  • A palpable defect at the site of rupture is usually felt just superior to the proximal pole of the patella.

  • Plain radiographs often demonstrate patellar baja, an avulsion of the superior pole of the patella, spurring of the superior patellar region, or calcification within the quadriceps tendon. Insall-Salvati Index is less than 0.8 (1).

  • MRI is a useful adjunct study because it can demonstrate partial ruptures or preexisting disease within the quadriceps tendon.


  • Often referred to as tennis leg.

  • Traumatic injury to middle-aged athlete presenting as sudden pain in posterior proximal calf region. Significant pain, swelling, and ecchymosis usually occur with 24 hours.

  • Involves tearing of the medial head of the gastrocnemius muscle typically at its musculotendinous junction (35).

  • Mechanism of injury combines ankle dorsiflexion in combination with knee hyperextension.

May 22, 2016 | Posted by in SPORT MEDICINE | Comments Off on Soft Tissue Knee Injuries (Tendon and Bursae)
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