Quick Summary
A dislocated or subluxating kneecap happens when your patella slips out of its groove at the front of the knee — usually towards the outside — causing sudden pain, swelling and a feeling that the knee may give way. Most first-time dislocations without a fracture or loose fragment are managed successfully without surgery, and research suggests structured physiotherapy is the most effective first-line approach. Our HCPC-registered physiotherapists in New Malden guide you through a phased programme to rebuild strength, control and confidence, typically over 6–12 sessions.
What Is Patella Dislocation and Subluxation?
Your kneecap (patella) normally glides within a shallow groove called the trochlea on the front of your thigh bone. In a lateral patellar dislocation, the kneecap comes fully out of this groove, almost always towards the outside of the knee. In a subluxation, it only partially slips and then corrects itself. Together these sit on a spectrum known as patellofemoral instability.
The medial patellofemoral ligament (MPFL) is the main soft-tissue restraint stopping the kneecap sliding sideways during the first 0–30 degrees of knee bend. Evidence shows this ligament is torn or stretched in the great majority of first-time dislocations, with MRI studies reporting MPFL rupture in around 98% of cases (Migliorini et al., Life, 2021).
Because the kneecap dislocates and then relocates, damage to the joint surface is common, and bleeding into the joint often causes rapid swelling. This is why a first-time dislocation should always be imaged before rehabilitation begins, so that a fracture or loose fragment can be excluded.
Several underlying factors make instability more likely: a shallow trochlear groove (trochlear dysplasia), a high-riding kneecap (patella alta), knock-knee alignment, generalised ligamentous laxity, weakness of the inner thigh muscle (vastus medialis obliquus), and tightness of the structures on the outer side of the knee. Trochlear dysplasia is the single most influential factor for repeat dislocation.
Do You Experience These Symptoms?
✓ A visible or felt “popping out” of your kneecap towards the outside of the knee, sometimes correcting itself
✓ Sudden, severe pain at the front of the knee at the moment of injury
✓ Rapid swelling within the first couple of hours, suggesting bleeding within the joint
✓ A sensation of the knee giving way, buckling or feeling unstable
✓ Difficulty straightening or bending the knee, or reluctance to put weight through it
✓ Tenderness along the inner border of the kneecap where the MPFL attaches
✓ Apprehension or anxiety when the kneecap is gently pushed outwards
These symptoms can be treated.
The sooner you begin, the better your chances of a smoother recovery.
What Causes Patella Dislocation?
• Traumatic twisting or a direct blow
Most first-time dislocations occur during sport when the knee is bent and the lower leg twists outwards with the foot planted.
A direct blow to the inner side of the kneecap can also force it towards the outside of the knee.
• Anatomical predisposition of the bones
A shallow trochlear groove and a high-riding kneecap reduce the bony containment that normally holds the patella in place.
These features are strongly associated with both a first dislocation and with repeat episodes.
• Malalignment of the leg
Knock-knee alignment and inward rotation of the thigh bone shift the line of pull on the kneecap outwards.
This dynamic loading pattern increases the tendency for the patella to track laterally.
• Soft-tissue and muscle factors
Generalised ligamentous laxity, weakness of the vastus medialis obliquus, and tightness of the iliotibial band and lateral retinaculum all reduce control of the kneecap.
These factors particularly explain recurrent subluxation and instability that occurs without a clear injury.
• Age, sex and previous dislocation
Adolescents and young adults are at the highest risk, and women are affected more often than men.
A previous dislocation in either knee, or a family history of instability, further raises the likelihood of recurrence.
How We Treat Patella Dislocation at J&J Therapy
Hands-On Manual Therapy
Gentle soft-tissue release for the tight structures on the outer side of your knee, careful patellar mobilisation, and hip and ankle mobility work to improve overall lower-limb mechanics — always alongside active rehabilitation.
Shockwave Therapy*
For conditions involving joint instability, acute ligament injury, or open growth plates in younger patients, our care emphasises specialised manual therapy and targeted exercises — the most appropriate approach for your specific needs.
Targeted Exercise Programme
A phased programme progressing from early quadriceps activation and range of motion, through hip abductor and rotator strengthening to control knee position, to neuromuscular retraining and criteria-based return to sport.
When to Seek Urgent Medical Help
While most symptoms are not serious, urgent medical attention is required if you experience any of the following:
A locked knee that cannot be straightened or bent, or a mechanical block to movement
Inability to bear weight, rapid tense swelling, or a suspected fracture
Numbness, pins and needles, coldness or loss of pulse below the knee
A first-time dislocation that has not yet been assessed and imaged
FAQs About Patella Dislocation
Will my kneecap dislocate again?
It may. A systematic review and meta-analysis found that roughly one in three people experience a further dislocation after a first episode, and that this risk rises substantially when several risk factors are present together, such as a shallow trochlear groove, a high-riding kneecap or open growth plates (Huntington et al., American Journal of Sports Medicine, 2020).
A structured strengthening and neuromuscular programme is designed to reduce that risk and improve your control and confidence.
Do I need surgery?
Most first-time dislocations without a fracture or loose fragment are managed successfully without surgery, with physiotherapy as the first-line treatment. Surgery such as MPFL reconstruction is usually reserved for recurrent instability, or when there is a loose fragment or high-risk anatomy.
Our physiotherapists will refer you promptly for an orthopaedic opinion if that is the right path for you.
How long until I can return to sport?
For a first-time dislocation treated without surgery, most people return to everyday activities within 6–8 weeks and to sport at around three months, although this depends on the severity of the injury and your individual progress.
We use strength and control benchmarks rather than time alone to decide when a return is appropriate.
Should I keep my knee completely still after a dislocation?
Generally no. Current evidence favours early, controlled movement over prolonged rigid immobilisation, which can lead to stiffness and muscle wasting (Smith et al., European Journal of Trauma and Emergency Surgery, 2010).
We may use taping or a supportive brace for comfort in the early stages, but the aim is to get you moving safely and rebuilding strength as soon as it is appropriate.
Do you use shockwave therapy for a dislocated kneecap?
No. We use our Swiss Storz Medical MASTERPULS radial shockwave device for certain chronic tendon conditions, but there is no evidence base supporting shockwave for kneecap instability, which is a mechanical problem of the ligaments and joint shape rather than a chronic tendon complaint.
It is also unsuitable where there is a fresh ligament injury or bleeding within the joint, and it is contraindicated over the open growth plates common in younger patients. Instead we focus on strengthening, neuromuscular retraining and a structured return-to-activity plan, which is what the research supports.
This page is for general information only and does not replace professional medical advice.
Reviewed by Lavya Arigalayan, MSc, HCPC Registered Physiotherapist.
Last reviewed:
2026년 8월 20일