Mechanism
- sudden forceful contraction of quadriceps during an attempt to stop
- more common in obese patients and those with pre-existing degenerative changes in tendon (DM, SLE, RA, steroid use, renal dialysis patients)
Clinical Features
- inability to extend knee
- patella in lower (“baja”) or higher ("alta") position with palpable gap above or below patella respectively
- may have an effusion
Investigations
- knee x-ray to rule out patellar fracture
Treatment
- surgical repair of tendon