Patellar Instability

Patellar instability is a problem in which the kneecap (patella) fails to stay centred on the front of the thigh bone as the knee bends and straightens. At worst it dislocates and needs to be put back. This page covers the structures involved, how doctors judge risk, the treatments and how surgery in turkey is arranged.

What is patellar instability?

Picture a train wheel on a rail. The kneecap should run in a shallow track at the end of the femur, held by ligaments on both sides and by the pull of the thigh muscle. When the track is shallow, the ligaments are loose or torn, or the pull is off-line, the wheel can jump the rail.

That event is a kneecap dislocation. A lesser slip, where the patella moves sideways and returns by itself, is a subluxation. Patellar instability covers both, along with the apprehension that the kneecap may go again.

Who is affected by patellar instability?

It is most common in adolescents and young adults, with a peak in the teenage years, and it is seen more often in girls and young women. Sports with sudden twisting or landing, such as football, basketball, gymnastics and dance, are typical triggers. Some people have a family history of loose joints or a shallow groove.

Older adults can also dislocate a kneecap after a fall, but anatomy plays a smaller role in that group.

How serious is patellar instability?

The first episode is painful and frightening, but the kneecap often returns to place, and serious long-term harm is not the norm. The concern is repetition. Every dislocation can chip cartilage on the back of the kneecap or on the femur, and a confident, active life can shrink to cautious walking.

How this page is organised

We start with anatomy, then describe symptoms, causes and the risk factors that doctors measure. Next come diagnosis, look-alike conditions, rehabilitation and home exercises. Surgical options and care abroad follow, and the page finishes with complications, prevention, outlook, common questions and sources. Our knee hub gives wider background.

The kneecap is a small bone held in place by a balance of bone shape, ligaments and muscle pull. Patellar instability appears when one or more of these supports fail. Knowing each one explains why two people with the same dislocation can need very different treatment.

What holds the kneecap in place?

The patella sits inside the tendon of the quadriceps. Below it the patellar tendon attaches to the shin bone at a bump called the tibial tubercle. As the knee bends, the kneecap glides into the trochlea, a V-shaped groove on the front of the femur.

Three kinds of support keep it central. Bone shape (the depth of the groove and the shape of the kneecap) works from 30 degrees of bend onward. Ligaments provide the stability in the first 20 to 30 degrees of bending. Muscles, especially the inner part of the quadriceps called the vastus medialis obliquus, dynamically steer the patella.

What is the medial patellofemoral ligament?

The medial patellofemoral ligament (MPFL) is a thin band running from the inner edge of the kneecap to the inner side of the femur. It is the main check against sideways movement toward the outer side, particularly in early bend, and it supplies more than half of the restraint in that range.

When a kneecap dislocates, the MPFL is torn or stretched in most cases. That is why recurrence is a risk after a first event.

What changes in patellar instability?

A torn or stretched MPFL allows the patella to travel too far. Repeated episodes stretch the supporting tissue even more and may wear the cartilage under the kneecap. Bone shape can add to the problem: a shallow trochlea (dysplasia), a high-riding kneecap (patella alta) or a tibial tubercle set too far out all increase the sideways pull.

How do the leg and hip contribute?

Rotation of the thigh and shin, knock-knee alignment and weak hip muscles can all line up to send the kneecap outward. This is why examination looks at the hip, the foot and walking pattern, not only the kneecap itself.

Doctors classify patellar instability by when it began, how often it occurs and which risk factors are present. These details determine whether rehabilitation is enough and which operation fits. A clear category also helps you compare notes with a surgeon abroad.

What are the main patterns?

What is the difference between dislocation and subluxation?

In a dislocation the patella leaves the groove fully and usually needs to be guided back. In a subluxation it slips partly and returns spontaneously. A person can have subluxations for years before a full dislocation, or may never dislocate fully but still lose confidence in the knee.

Which risk factors do surgeons measure?

The Dejour classification grades trochlear dysplasia from type A to D on X-ray and MRI. Surgeons also measure patella height (using indices such as Caton-Deschamps) and the distance between the tibial tubercle and the trochlear groove (TT-TG), where a distance above about 20 mm suggests the tubercle sits too far out.

The more risk factors present, the higher the chance of repeated dislocation, and the more likely a combined operation is needed instead of ligament reconstruction alone.

How does age change the picture?

In growing children the growth plates limit which bone operations are safe, so ligament and soft tissue procedures are favoured. In adults, bone realignment can be added when measurements justify it.

Patellar instability is diagnosed from the story, a careful examination and imaging that checks bone shape and injury to cartilage. After a first dislocation, the main aim is to find any fragment that needs surgery. After repeated events, the aim shifts to measuring risk factors.

What happens at the first assessment?

If the kneecap is still out of place, a clinician will usually straighten the knee and guide it back, often with pain relief. An X-ray is taken before or after to look for a fracture. The knee is then protected in a brace and you are told how much weight to bear.

What does the doctor ask?

The history covers how it happened, whether the kneecap went out and back, whether you have ever had a similar episode and whether other family members have loose joints. Questions about sport, work and previous operations help to judge demand.

What does the examination involve?

The clinician looks at the way you stand and walk, checks for swelling and feels for tenderness along the inner side of the kneecap. The apprehension test gently pushes the patella outward while the knee is slightly bent, and a positive test makes you tense up. Glide tests judge how far the kneecap travels.

Hip rotation, foot posture and flexibility of the hamstrings and calves are checked, and general joint laxity is scored.

Which imaging is used?

X-rays show the shape of the groove, patella height and any fracture. MRI shows the MPFL tear, bone bruising, cartilage injury and loose fragments. CT may be used to measure TT-TG distance and rotation, especially if bone surgery is planned.

What should you bring to a remote review?

Send the MRI images (not only the report), X-rays taken from the side and in skyline view, any CT, operation notes if you have had surgery and a short history of each episode with dates. Our medical record review guide lists the steps. A surgeon abroad can only judge your risk factors with the images themselves.

Most first-time kneecap dislocations without a loose fragment are treated without surgery, and many people recover well. The programme combines early protection, a return of movement and long-term muscle training. It usually runs 3 to 6 months, and there is no single perfect protocol.

What happens in the first two weeks?

After the kneecap is back in place, swelling and pain are the first concerns. Rest, ice wrapped in a cloth, elevation and simple pain relief help. A hinged brace or a patellar stabilising sleeve gives support, and crutches may be used for a few days until you can walk without limping.

If the knee was locked or very swollen, an MRI is usually arranged within days to rule out a loose fragment.

How is movement restored?

Gentle range-of-motion work starts early. Many protocols allow 0 to 90 degrees of bend for the first weeks, then progress to full movement as swelling settles. Stationary cycling at low resistance is a common early exercise.

What strengthening is used?

The programme builds the thigh (quadriceps), the hip abductors and rotators, the buttock muscles and the calf. Work on the hip is important because it controls inward collapse of the knee. Typical stages are:

• Weeks 0 to 2: protect, reduce swelling, regain extension.
• Weeks 2 to 6: straight-leg and closed-chain work, hip side lifts, balance on one leg.
• Weeks 6 to 12: step-downs, split squats, resisted bands and controlled landings.
• Months 3 to 6: sport-specific drills, cutting and jumping once strength tests are satisfactory.

Do braces and taping help?

A patellar stabilising brace with a lateral buttress, or tape, can improve confidence and reduce the chance of slipping. Studies suggest they give modest benefit, and they do not correct bone shape. They are best treated as an aid during rehabilitation or return to sport.

What medicines are useful?

Simple pain relievers and short courses of anti-inflammatory medicines help in the early phase. They do not fix instability. Ask your doctor about safe use, particularly if you have stomach, kidney or heart problems.

What does the evidence say about surgery versus rehabilitation?

Trials of first-time dislocation show that rehabilitation is a reasonable first choice for most people, though some surgical groups report fewer repeat dislocations. About 1 in 2 or more people with risk factors such as a shallow groove, a high-riding kneecap or youth may dislocate again. Your surgeon will weigh your risk factors.

When do you move on from non-surgical care?

Move on when the kneecap dislocates again, when you feel constant apprehension despite good strength, or when a fragment is present on scans. For many people, a second dislocation changes the conversation about surgery.

Surgery for patellar instability aims to restore the checks that hold the kneecap in line and to treat associated injuries. The procedures linked to this condition are MPFL reconstruction, knee arthroscopy and cartilage restoration. Often more than one is used in the same operation.

What is MPFL reconstruction?

MPFL reconstruction replaces the torn medial patellofemoral ligament with a graft, usually a hamstring tendon from your own leg or a donor tendon. The graft is anchored on the inner side of the kneecap and on the femur at a carefully chosen point. It is the most common surgery for recurrent patellar dislocation. You can read about MPFL reconstruction in turkey and our MPFL reconstruction cost guide.

It works best when bone shape is reasonably normal. If risk factors are severe, a bone procedure may be added.

When is arthroscopy needed?

Knee arthroscopy uses keyhole cuts to look into the joint. In patellar instability it can remove loose bodies, fix or trim cartilage flaps and check how the kneecap tracks. The details for knee arthroscopy in turkey and the cost guide are available.

What about cartilage restoration?

A dislocation can chip cartilage on the kneecap or femur. When the defect is large or sits in a load-bearing area, cartilage restoration may be combined with stabilisation. Techniques include fixation of a fragment, marrow stimulation, grafts or cell-based repair. See cartilage restoration in turkey and the cost guide.

Which bone procedures are used with soft tissue surgery?

If the tibial tubercle sits too far outward, a tibial tubercle osteotomy moves it inward and may lower it. If the groove is very shallow, a trochleoplasty reshapes it. These operations are done only in selected patients, mostly after growth is complete, and they lengthen recovery.

How do the options compare?

What are the usual outcomes?

Studies of MPFL reconstruction suggest that most patients have a stable kneecap and report good function, with a low rate of repeat dislocation. Results are best when risk factors are addressed in the same plan.

Not every kneecap dislocation can be prevented, but good conditioning lowers the odds and helps you recover better. Anatomy such as a shallow groove cannot be changed without surgery, so prevention focuses on muscle control and movement habits.

How can you lower the risk of a first dislocation?

• Strengthen the hips and thighs: good muscle control keeps the knee aligned over the foot.
• Practise landing: land softly with knees bent and pointing over the toes, not collapsing inward.
• Use warm-up programmes: neuromuscular warm-ups in team sport reduce knee injuries in trials.
• Choose suitable shoes and surfaces: avoid sticky surfaces that grip while the body turns.
• Know your family history: if close relatives dislocated kneecaps, ask for a screening at sports clinics.

How do you prevent another dislocation?

Complete rehabilitation, even when the knee feels well. Keep up hip and thigh strength for at least a year, and use a stabilising brace in high-risk sport if advised. If you notice apprehension, see a specialist early, since fixing the problem before more cartilage damage is easier than after.

What cannot be prevented?

You cannot change bone shape, inherited joint laxity or sudden contact accidents. For these, early assessment helps. Learning about ACL tears and patellofemoral pain syndrome may also help you notice related knee problems.

Can children and teenagers prevent it?

Growing bodies change quickly, so alignment and muscle balance can shift within a single season.

Young people with loose joints benefit from regular strength and balance training. Parents should seek an assessment after the first dislocation, since the earliest period is when guidance matters most.

The outlook for patellar instability is generally good when risk factors are recognised and rehabilitation is completed. Many people return to normal life and sport, though some need surgery to be confident. The path differs between a one-off event and a recurrent problem.

What is the natural history?

After a first dislocation, many people recover without further episodes, though a sizeable minority dislocate again. Risk is higher in teenagers, those with a shallow groove or high-riding kneecap, and those with lax joints. After several episodes, the chance of future dislocation is high without treatment.

What is recovery like after MPFL reconstruction?

These are general ranges. Combined bone procedures often add several weeks.

How long do results last?

Studies of MPFL reconstruction report that most patients maintain a stable kneecap for many years, with high satisfaction. Long-term cartilage health depends on the initial damage and how well alignment was addressed.

Can you return to sport?

Most people who complete rehabilitation return to sport, though a share do not return to their previous level because of fear or other injuries. Confidence tests and strength symmetry above about 90% are commonly used to clear return.

What helps the best result?

Early diagnosis of risk factors, an operation tailored to your anatomy, careful graft placement and committed physiotherapy. For a view of your own case, send your scans through the free case review. You might also read about knee cartilage damage and knee osteoarthritis to understand long-term risks.