KNEE · CONDITIONS & TREATMENT
Patellar Dislocation & Instability
Understanding cartilage injury, loose bodies, MPFL reconstruction, TTO and DFO—and when nonsurgical care may be enough.
A Kneecap Dislocation Does Not Always Need Surgery
The patella can slide out of its groove, usually toward the outside of the knee. A first dislocation may be managed without surgery when there is no displaced cartilage or bone fragment and the risk of repeat instability is acceptable. Recurrent dislocations, persistent instability or an important cartilage injury change the discussion.
[1]A kneecap that remains dislocated needs prompt medical care. Even if it slips back into place, an assessment is important to identify associated damage.
Evaluate the Cartilage as Well as the Ligament
Examination and X-rays assess the kneecap, fractures and alignment. MRI helps identify injury to the medial patellofemoral ligament (MPFL), cartilage damage and loose fragments. Large swelling after a dislocation can signal an injury to the joint surface. Standing alignment films and selected CT imaging may help assess bony contributors.
[2]The evaluation also considers a shallow groove, a high-riding patella, the pull of the patellar tendon and knock-kneed alignment. These findings help explain why the kneecap dislocated and which problems need treatment.
[1]When Nonsurgical Care Is Reasonable
A brace or short period of support, swelling control and guided rehabilitation may be used after a suitable first-time injury. Therapy addresses motion, quadriceps and hip strength, balance and movement control. The plan includes reassessment for ongoing apprehension or giving-way.
[1]Surgical Options: Each Treats a Different Problem
| Procedure | What it addresses | When it may be considered |
|---|---|---|
| Cartilage fragment fixation or loose body removal | A displaced piece of cartilage, sometimes with attached bone. | A viable, repairable fragment may be fixed back in place. A fragment that cannot be restored may be removed, particularly if it causes catching or locking. |
| MPFL reconstruction | The damaged soft-tissue restraint on the inner side of the kneecap. | Recurrent instability or selected high-risk first injuries; stabilization may be combined with surgery for a displaced cartilage fragment. |
| Tibial tubercle osteotomy · TTO | The direction of the patellar tendon’s pull and pressure on the kneecap cartilage. | Selected maltracking, a lateralized attachment or a high-riding patella. Moving the attachment can improve tracking and, in suitable cases, unload a damaged cartilage area. |
| Distal femoral osteotomy · DFO | Significant knock-kneed alignment arising from the thighbone. | Selected patients whose valgus alignment contributes to instability or overload; it may be combined with stabilization or cartilage treatment. |
| Cartilage repair or restoration | A remaining defect in the patella or the groove’s joint surface. | If fragment fixation is not possible, defect size, depth, location and bone involvement guide restoration options. |
Protect the Joint Surface Whenever Possible
Loose body removal is not automatically the best answer: preserving a substantial repairable fragment may restore the original surface. If a defect remains, options can include cell-based restoration such as MACI or an osteochondral graft. Cartilage treatment may be performed with stabilization and unloading procedures, either together or in stages.
[3][5]Compare knee cartilage restoration options →
Match the Operation to the Anatomy
MPFL reconstruction alone cannot correct every bony contributor. Conversely, not every dislocation requires a TTO or DFO. Relevant anatomy, cartilage findings and skeletal maturity guide the combination. Open growth plates require different techniques and can limit standard bony procedures.
[3]Recovery Depends on What Is Repaired
Cartilage work or an osteotomy can require more protection than ligament surgery alone. Weight-bearing, brace use and return to sport follow the actual operation and healing progress. Risks include stiffness, persistent pain, recurrent instability and, with bone procedures, delayed healing or symptomatic hardware.
[1][4]Questions for Your Visit
- Is there a cartilage fragment that can be saved?
- Is my instability mainly ligament-related, or are alignment and tracking contributing?
- Would cartilage restoration, a TTO or a DFO improve the plan?
Sources & Further Reading
Evidence checked October 3, 2026. General education; treatment is individualized after an examination.
- AAOS OrthoInfo — Unstable kneecap
- ESSKA — First-time patellar dislocation consensus, evaluation (2025)
- ESSKA — First-time patellar dislocation consensus, treatment (2025)
- AAOS surgical education — Combined DFO, TTO and MPFL reconstruction
- AAOS surgical education — Patellar MACI with TTO and MPFL reconstruction