Patellar dislocation
 | The article's lead section may need to be rewritten. (September 2009) |
| Patellar dislocation | |
|---|---|
| Specialty | Rheumatology  |
Patellar dislocations occur with significant regularity, particular in young female athletes.[1] It involves the patella sliding out of its position on the knee, most often laterally, and may be associated with extremely intense pain and swelling.[2] The patella can be tracked back into the groove with an extension of the leg, and therefore sometimes returns into the proper position on its own.[2]
Anatomy of the knee
The patella rests in the patellofemoral groove, a cavity located on the knee between the distal femur and the tibia. The sides of the patella attach to certain ligaments and tendons to stabilize and support it. The superior border of the patella attaches to the common tendon of the quadriceps muscles,[2] the medial borders are attached to the vastus medialis muscle, and the inferior border is connected to the tibial tuberosity. The main ligament stabilizer, the patellofemoral ligament, rests directly over the femur and the patella while the lateral and medial collateral ligaments act as the secondary ligament stabilizers from either side of the patella.[2]
Mechanism of injury
Patellar dislocations occur in 2 ways:
- Direct blow to the kneecap knocking the patella out of place
- Awkward twisting motions of the knee[2]
Sports commonly associated with patellar dislocation include soccer, gymnastics and ice hockey. The patella wobbles out of the patellofemoral groove, usually to the lateral side of the knee (away from the middle of the body).[2] This occurs when the quadriceps tendons and other ligament stabilizers attached to the borders of the patella contract forcefully as the knee is rotating, pulling the patella out of place.[2]
Predisposing factors
1) Demographics
Age:
• Average age of occurrences for patellar dislocation is 16–20 yrs old[3]
• Primarily due to increased participation in sports and recreation
Gender:
• Female are more susceptible to patellar dislocation
Athletic Population [3]:
• Particularly in sports with twisting, rotational motion of the knee
• Direct trauma to the knee
2) Positive Family History
• Related up to 24% of patellar dislocation incidences[2]
3) Anatomical Factors
Excessive Q-angle
• Angle greater than 25 degrees between the patellar tendon and quadriceps muscle[4]
Misalignment of the patella on the knee joint
• Due to malformed patella/knee joint, patella situated abnormally higher on the knee than normal[4]
Insufficient Vastus Medialis Obliquus Muscle (VMO)[2])
• Normal function is to keep patella in stable position
• If function is decreased, will result in instability of the patella
Symptoms and signs
There will be swelling and impaired mobility following patellar dislocation.[5] Pain is usually described as being “inside the knee cap”. If displaced, the leg would have a tendency to flex even when relaxed.[2]
To assess the knee, the Patellar Apprehension Test may be done in which the patella is moved back and forth while the knee is flexed at approximately 30 degrees.[5]
Also, a patella tracking assessment can be performed by the patient making a single leg squat and stand or, alternatively, lying supine with knee extended from flexed position. A patella that abruptly deviates medially on early flexion is called the J sign, and indicates imbalance between vastus medialis and lateral forces.[6]
Treatment options
Most people are able to pop the patella back into place, in which a “snap” is heard upon complete leg extension.
Two types of treatment options are typically available:
•surgery (open or arthroscopic)
•conservative treatment (rehabilitation).
Regardless of the treatment option chosen, a rehabilitation program of usually 6–16 weeks will follow.[7] Choosing an appropriate treatment depends on a number of factors, including associated injuries with bone fragments or injuries to the soft tissues around the knee. Also things like the patients age, sports and activities they participate in, level of competition, and time needed to return to work and/or sport participation are all very important factors to consider. According to most research, surgery is strongly suggested in cases where other structures in the knee are severely damaged, or specifically when there is: [7]
• Concurrent osteochondral injury
• Continued gross instability
• Palpable disruption of the medial patellofemoral ligament and the vastus medialis obliquus
• High-level athletic demands coupled with mechanical risk factors and an initial injury mechanism not related to contact
Research appears to indicate that the conservative approach, avoiding surgery, is the preferred method of treatment wherever possible.[4][8][7] In comparing the rates of re-injury, function of the knee, and patients subjective opinions of their knee function and stability, the best available evidence found no significant differences between surgical and conservative treatments[4][7] This suggests surgery is much less desirable, as there are inheritant complications that can arise from surgery, such as adverse reaction to anesthesia, as well as infections.[8] In particular, surgery for children or adolescents who have not completely matured skeletally are contraindicated, as there is a risk that surgery may injure growth structures in the knee.[8][7]
Supplements like glucosamine and NSAID's could be used to keep the knee strong.[5]
Post-treatment rehabilitation
Due to the high rates of patellar re-dislocations, patients will normally undergo a rehab program regardless of the treatment chosen. The rehab program will be aimed at reducing the chances of re-injury or any other knee related injuries, such as Patellofemoral pain syndrome. Maintaining movements about the injured joint can reduce pain, and maintain the health of the muscles and tissues around the knee joint.[5]
See also
References
- ^ Palmu, S., Kallio, P.E., Donell, S.T., Helenius, I., & Nietosvaara, Y. (2008). Acute patellar dislocation in children and adolescents: A randomized clinical trial. Journal of Bone and Joint Surgery. 90: 463-470.
- ^ a b c d e f g h i j Dath, R., Chakravarthy, J., & Porter K.M. (2006). Patella Dislocations. Trauma, 8, 5-11.
- ^ a b Atkin D.M., Fithian, D.C., Marangi, K.S., Stone, M.L., Dobson, B.E., & Mendelsohn, C. 2008. Characteristics of Patients with Primary Acute Lateral Patellar Dislocation and Their Recovery Within the First 6 Months of Injury. American Journal of Sports Medicine, 28: 472
- ^ a b c d Buchner, M., Baudendistel, B., Sabo, D., & Schmitt, H. (2005). Acute traumatic patellar dislocation: Long- term results comparing conservative and surgical treatment. Clinical Journal of Sports Medicine. 15: 62-66.
- ^ a b c d Brukner, P., & Khan, K. (2006). Clinical Sports Medicine (3rd Edition). Sydney (Australia): McGraw-Hill.
- ^ Family Practice Notebook > Patella Tracking Assessment by Scott Moses, last revised before 5/10/08
- ^ a b c d e Shea, K.G., Nilsson, K., & Belzer, J. (2006). Patellar dislocation in skeletally immature athletes. Operative Techniques in Sports Medicine. 14: 188-196.
- ^ a b c Nikku, R., Nieteosvaara, Y., Kallio, P.E., Aalto, K., & Michelsson, J.E. (1997). Operative vs. closed treatment of primary dislocation of the patella: Similar 2-year results in 125 randomized patients. Acta Orthopaedica. 68: 419-423.