Patellar Tendon Rupture: Pathogenesis and clinical findings
Author:
Molly Joffe
Reviewers:
Liam Thompson, Alyssa Federico, Tara Shannon, Gentson Leung* *MD at time of publication
Chronic disease (e.g. renal failure, gout, rheumatoid arthritis, and diabetes)
Repetitive activities involving rapid knee flexion and extension
Tendon inflammation and micro-tearing
Fluoroquinolone (antibiotic class) use
Smoking
Immobilization of knee
↓ Muscle and tendon flexibility and strength
Steroid use (including intraarticular injections)
Changes in collagen fibrils composing tendon (exact mechanism unknown)
Disrupted blood supply to tendon and poor healing
Compromised integrity and strength of the tendon
Sudden heavy load on flexed knee while foot is planted
Quadriceps muscles contract while lengthening (eccentric contraction)àforce exceeds tendon strength
Patellar tendon innervated by common peroneal (fibular) nerve
Nociceptors (pain receptors) within tendon activated by tendon rupture
Pain and tenderness below the patella
Collagen fibres in tendon tear
Tearing or popping sensation at time of injury
Patellar Tendon Rupture
Tendon/Ligament detaches from bony attachment on patella or tibial tubercle No connection of quadriceps to tibia via patellar tendon
↑ Force on tibial tubercle during tendon detachment
Avulsion fracture of tibial tubercle
Trauma to tendon ruptures surrounding blood vessels
Coagulation cascade and inflammatory mediators released at rupture site
Quadriceps muscles unable to stabilize patellar tracking
Instability of knee joint
Quadriceps muscle tension pulls patella upwards with no resistance from patellar tendon
Patellar tendon cannot use distal attachment site for leverage
Knee extensor muscles unable to effectively contract
Knee buckling
Abnormal gait
Patella alta
(high sitting patella) on X-ray
Palpable gap below the patella
Bruising below the patella
Swelling below the patella
↑ Risk of falls
Loss of patellar reflex
Inability to perform a straight leg raise (hip flexes and knee cannot remain straight)
Hematoma (blood collection under the skin)
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published August 28, 2022 on www.thecalgaryguide.com