A patella baja (or patella infera) is an abnormally low lying patella, which is associated with restricted range of motion, crepitations and retropatellar pain 4. If long standing extensor dysfunction may ensue with significant morbidity. It is seen in a variety of clinical scenarios including 1:
- quadriceps dysfunction
- tourniquet paralysis
- bony or ligamentous trauma
- tibial tubercle transplant
- ACL repair
- total knee replacement : seen in 25% of patients 1
- achondroplasia : usually asymptomatic
A number of methods for determining patella height have been devised 2-3:
- Insall-Salvati ratio - according to the relative height of the patella and length of the patellar tendon. It is assessed on lateral radiographs or sagittal cross-sectional imaging.
- Blackburne-Peel ratio - ratio of vertical distance between tibial plateau and patellar articular surface and length of the patellar articular surface.
- Norman, Egund and Ekelund method
- Caton-Linclau method
- Blumensaat's technique
It is important in the setting of previous surgery to ensure that the patella has not been resected, as change in patellar morphology will clearly affect the ratio 1.
Patella baja, when post traumatic / surgical is uncommonly asymptomatic and requires early surgical correction as conservative measures are rarely successful 4. Treatment requires either a tibial tuberosity osteotomy 4 and re-implantation proximally or patellar tendon lengthening 5.
- 1. Weale AE, Murray DW, Newman JH et-al. The length of the patellar tendon after unicompartmental and total knee replacement. J Bone Joint Surg Br. 1999;81 (5): 790-5. J Bone Joint Surg Br (link) - Pubmed citation
- 2. Scuderi Giles R. The Patella. Springer, 1995. ISBN: 0387943714, 9780387943718.
- 3. Blackburne JS and TE Peel. “A new method of measuring patellar height.” Journal of Bone and Joint Surgery - British Volume 59-B, no. 2 (May 1, 1977): 241-242. [Link].
- 4. Malek M. Mike. Knee surgery. Springer, 2001. ISBN: 0387982949, 9780387982946.
- 5. In Y., S.-J. Kim and Y.-J. Kwon. “Patellar tendon lengthening for patella infera using the Ilizarov technique.” J Bone Joint Surg Br 89-B, no. 3 (March 1, 2007): 398-400. doi:10.1302/0301-620X.89B3.18586.
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Low lying patella||✓|