What is Patellofemoral Crepitus?
Patellofemoral crepitus is a grating, crackling, or popping sensation or sound produced by the patellofemoral joint during knee movement, which can occur as a normal physiological phenomenon in healthy knees or as a pathological finding in patients with knee disorders. 1, 2
Clinical Characteristics
Crepitus represents vibration signals produced by the knee joint during motion, which can be measured objectively through vibration arthrometry techniques. 2
In pathological states, crepitus results from peripatellar fibrosynovial hyperplasia at the junction of the superior pole of the patella and distal quadriceps tendon, which becomes entrapped within the intercondylar box of the femoral component during knee flexion. 1
The sensation occurs when the knee extends and the fibrosynovial tissue exits the intercondylar box, creating the characteristic crepitant feeling or audible sound. 1
Distinction from Patellofemoral Pain Syndrome
Patellofemoral stress syndrome (pain syndrome) is specifically defined as peripatellar pain WITHOUT clinical evidence of patellofemoral crepitus, distinguishing it as a separate clinical entity. 3
The absence of crepitus is a diagnostic criterion that helps differentiate patellofemoral pain syndrome from other knee pathologies. 3
Clinical Context and Significance
Physiological patellofemoral crepitus can occur in normal, healthy knees without pain or pathology, representing benign joint sounds during movement. 2
Pathological crepitus is most commonly associated with posterior-stabilized total knee arthroplasty, with reported incidence ranging from 0% to 18% depending on implant design. 1, 4
In osteoarthritis, crepitus patterns can indicate the condition of patellar-femoral joint cartilage, with different vibration signal characteristics corresponding to varying degrees of cartilage degeneration. 2
Post-Surgical Crepitus
Following total knee arthroplasty, crepitus occurs in 0.55% to 9.4% of patients depending on femoral component design, with older designs showing substantially higher rates. 4
Most patients with post-arthroplasty crepitus are unaware of the problem or have minimal symptoms, requiring no treatment in the majority of cases. 1
When crepitus causes significant disability after arthroplasty, recurrence rates are high (45.7%) even after arthroscopic debridement, with 17.1% requiring repeat surgical intervention. 5