Patellar instability occurs when the kneecap (patella) slips partially out of place (subluxation) or fully dislocates from its groove in the femur (trochlea). This often happens during twisting injuries, sudden changes of direction, direct impacts, or awkward landings. Some patients experience a single traumatic episode, while others have recurrent instability due to underlying anatomic factors such as trochlear dysplasia (an abnormally shaped or shallow groove), patella alta (a high-riding kneecap), ligament laxity, or increased tibial tubercle–trochlear groove (TT–TG) distance.
Patellar instability is most common in adolescents and young adults, especially athletes. Typical symptoms include pain, swelling, a sense that the kneecap “slips,” “shifts,” or “pops out,” difficulty with stairs, and apprehension during pivoting or squatting. After a dislocation, many patients describe the knee swelling rapidly and difficulty walking.
Proper diagnosis and treatment planning are important—untreated recurrent instability can damage the cartilage on the underside of the patella and lead to long-term pain or arthritis.
Evaluation begins with a detailed history and physical examination. Dr. José Vega will assess for tenderness along the medial patellofemoral ligament (MPFL), patellar mobility, the J-sign, limb alignment, rotational factors, and strength of the quadriceps—especially the vastus medialis obliquus (VMO).
Standing X-rays evaluate patellar height, alignment, and evidence of prior dislocations. MRI is essential after a first-time dislocation because it can reveal:
- MPFL tears
- Bone bruising patterns
- Loose cartilage or osteochondral fragments
- Trochlear dysplasia
- Patella alta
- TT–TG distance abnormalities
In some cases, a CT scan may be recommended to accurately quantify the TT–TG distance or assess trochlear anatomy when surgical planning is being considered.
Understanding these anatomic factors is crucial, as they determine which treatment—nonoperative or surgical—will provide the most durable stability.
Yes—many patients with a first-time patellar dislocation and no loose cartilage fragments can begin with nonsurgical care.
Bracing
A patellar-stabilizing brace supports the kneecap and reduces lateral translation during early healing. It may be worn for several weeks during walking and activity.
Physical Therapy
Therapy is essential and focuses on:
- Strengthening the quadriceps, particularly the VMO
- Improving hip abductor and core strength
- Enhancing balance and neuromuscular control
- Stretching tight lateral structures
- Correcting faulty movement patterns during squatting, landing, and cutting
A well-executed therapy program often lasts 8–12 weeks.
Activity Modification
Avoiding twisting, pivoting, and high-impact movements early in recovery reduces the risk of repeat instability.
While many patients recover well after a first-time dislocation, recurrent instability is common—especially in patients with underlying anatomic risk factors.
Surgery is recommended when:
- The patient has recurrent instability
- A first-time dislocation results in a loose osteochondral fragment
- Imaging identifies high-risk anatomy (e.g., severe trochlear dysplasia, patella alta, significant TT–TG distance)
- The knee remains apprehensive or unstable after a full course of physical therapy
- The patient desires to return to high-level sports safely
Surgical treatment is tailored to the individual’s anatomy and may involve one or more procedures to correct instability.
Medial Patellofemoral Ligament (MPFL) Reconstruction
The MPFL is the primary soft-tissue restraint that prevents the patella from dislocating laterally. When it is torn or stretched out, reconstruction with a tendon graft (hamstring or allograft) can restore stability. This is the cornerstone procedure for recurrent instability.
MPFL reconstruction is highly effective, especially when bony alignment is normal.
Tibial Tubercle Osteotomy (TTO)
A TTO entails using a small saw to cut the tibial tubercle (where the kneecap attaches to the shin bone through the patellar tendon) from the rest of the tibia so that it can be repositioned in a better location. A TTO is performed when the patella tracks too far laterally or sits too high, often due to an elevated TT–TG distance or patella alta. The tibial tubercle is repositioned (medialized and/or distalized) to improve patellar tracking and decrease instability forces.
TTO is commonly combined with MPFL reconstruction in patients with significant malalignment.
Trochleoplasty
In cases of severe trochlear dysplasia, a trochleoplasty creates a deeper groove for the patella to track within. This is a specialized procedure reserved for select patients and typically performed alongside MPFL reconstruction, with or without a concomitant tibial tubercle osteotomy.
Cartilage Procedures
If the dislocation caused a cartilage injury or loose fragment, additional procedures such as cartilage fixation, osteochondral transplant, or MACI may be performed.
After surgery, patients usually follow:
- 6 weeks in a stabilizing brace
- Gradual increase in weight-bearing
- Progressive range-of-motion exercises
- Quadriceps and hip strengthening
- Neuromuscular control training
Return to running generally begins around 3–4 months, with full return to sports at 6–9 months, depending on the extent of the procedure and rehab progress.
Patellar instability can be painful, frustrating, and limiting—especially for active individuals. Fortunately, modern treatment options offer excellent outcomes. Whether managed with nonsurgical rehabilitation or advanced procedures such as MPFL reconstruction, tibial tubercle osteotomy, or trochleoplasty, most patients can return to full activity with restored confidence and stability.
If you are experiencing recurrent kneecap dislocations, feelings of instability, or pain during activity, please contact Dr. José Vega’s office in Cleveland to schedule a consultation. Together, we can review your imaging, discuss your goals, and design a personalized treatment plan to stabilize your kneecap and protect your long-term knee health.
References
- Bernstein M, Bozzo I, Patrick Park J, Pauyo T. Patellofemoral Instability Part II: Surgical Treatment. J Am Acad Orthop Surg. 2024;32(20):e1035-e1046.
- Hurley ET, Colasanti CA, Anil U, et al. Management of Patellar Instability: A Network Meta-analysis of Randomized Control Trials. Am J Sports Med. 2022;50(9):2561-2567.
- Pauyo T, Park JP, Bozzo I, Bernstein M. Patellofemoral Instability Part I: Evaluation and Nonsurgical Treatment. J Am Acad Orthop Surg. 2022;30(22):e1431-e1442.
- Schneider DK, Grawe B, Magnussen RA, et al. Outcomes After Isolated Medial Patellofemoral Ligament Reconstruction for the Treatment of Recurrent Lateral Patellar Dislocations: A Systematic Review and Meta-analysis. Am J Sports Med. 2016;44(11):2993-3005.
- Weber AE, Nathani A, Dines JS, et al. An Algorithmic Approach to the Management of Recurrent Lateral Patellar Dislocation. J Bone Joint Surg Am. 2016;98(5):417-427.
At a Glance
Dr. Jose Vega
- Board-certified orthopedic surgeon
- Fellowship-trained sports medicine specialist
- Author of industry leading peer reviewed publications
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