The patellofemoral joint is the area between the patella (kneecap) and the thigh bone (femur). There is a groove at the front of the thigh bone called the trochlea which guides the patella to slide vertically as the knee bends.
The patella is attached to the quadriceps muscle at the front of the thigh. The patella tendon runs from the lower end of the patella down onto the tibia or shin bone. The bony prominence where it attaches is called the tibial tuberosity.
Patients who have patella instability commonly describe one or more of the following symptoms:
- The patella fully dislocates out onto the outer aspect of the knee, this may require help to put it back in place.
- A feeling that the patella is going to dislocate or that it ‘subluxes’ or partially comes out of place.
- There may have been an accident or blow to cause the first dislocation or it may happen spontaneously.
- Recurrent instability happens when the patella feels unstable on many occasions, this is often accompanied by a general lack of confidence in the knee.
- Instability may also be accompanied by anterior knee pain, which can get worse after many dislocations.
- Patients may have problems with hyper-mobility and dislocation of other joints like the shoulders and elbows.
- Some patients have other family members with similar problems.
Patients who have patellofemoral pain commonly describe one or more of the following symptoms:
- Pain around the area of the patella at the front of the knee
- Pain just below the patella in the area of the patella tendon.
- The pain may be a constant dull ache, it may be worse with activity and sometimes accompanied by sharp pains.
- The pain is often worse with walking downhill or downstairs
- The pain is often worse with running and jumping type sports and cycling.
- Squatting and kneeling are often painful.
- The pain and stiffness can be worse after prolonged sitting with the knees bent up, such as in the car or at the cinema.
- There may be a cracking or grinding feeling or noise that comes from the front of the knee.
Why do I have Patella Instability?
Anyone may suffer patella instability if they have an accident that knocks the patella out of joint.
Some patients are much more likely to suffer problems with instability or recurrent patella instability if they have one or more of the following
- Hypermobility – where the soft tissues around the joints allow more movement that expected.
- Patella Alta – here the kneecap sits about 15mm higher than the normal which means it is above the groove that would normally act to constrain it.
- Trochlear Dysplasia – here the concave groove at the front of the femur is either shallow, flat or even convex, so there is no groove to guide the movement of the patella as the knee bends and it is more prone to dislocate. This is often a familial condition.
Why do I have Patellofemoral pain?
Patellofemoral joint pain can happen for a number of reasons. Some of the commonest reasons are listed here:
- Instability – when the patella dislocates it stretches and injures the surrounding soft tissues. Over time many dislocations can damage the smooth gliding cartilage surfaces of the patellofemoral joint resulting in pain from arthritis.
- Patella Alta – here the kneecap sits about 15mm higher than the normal, unfortunately this position puts a lot of stress on the joint resulting in overload and pain to the top end of the patella tendon or bottom of the patella.
- Trochlear Dysplasia – here the concave groove at the front of the femur is either shallow, flat or even convex. This results in a different sliding pattern of the kneecap as the knee bends and increased wear of the smooth gliding cartilage of the patellofemoral joint and pain from arthritis.
- Arthritis – despite no issue with the shape of the joint, the smooth gliding cartilage surfaces of the knee joint can still become damaged resulting in arthritic pain.
- Obesity – Carrying extra weight puts extra pressure on the knee joint, particularly the patellofemoral joint, resulting in pain and a higher chance of developing arthritis.
What can I do to help my patella instability?
The first time the kneecap dislocates it often requires help from the paramedics to put it back in place. Usually this results in a trip to A+E for assessment and X-rays to check there is no fracture. Later on patients might be seen in the fracture clinic and referred on for physiotherapy.
We try to avoid using knee braces for patients as they tend to hold the knee straight, which is the least stable position for the kneecap and it does not promote normal muscle functioning.
Physiotherapy can help to strengthen the muscles of the legs, core and gluteal muscles and alleviate symptoms. Maintaining an active lifestyle and achieving a heathy BMI is helpful.
Despite this some patients will continue to dislocate and will be referred to an orthopaedic knee surgeon who specialises in treating patellofemoral conditions.
The commonest operations used to treat recurrent patella instability are
- MPFL reconstruction
- MPFL reconstruction with tibial tubercle osteotomy
- Trochleoplasty (less common)
What can I do to help my patellofemoral pain?
Patellofemoral pain tends to start gradually and can begin at any time, even in childhood. A targeted physiotherapy assessment and programme of muscle strengthening for the muscles of the thigh, buttocks and core is usually the initial treatment.
Knee braces are not helpful for this condition. We would not usually recommend steroid injections for this condition.
Maintaining an active lifestyle and achieving a heathy BMI is helpful.
Despite this some patients will continue to suffer disabling anterior knee pain and will be referred to an orthopaedic knee surgeon who specialises in treating patellofemoral conditions.
The commonest operations used to treat recurrent patellofemoral pain are
- Tibial Tubercle osteotomy
- MPFL reconstruction with tibial tubercle osteotomy
- Patellofemoral partial knee replacement
Post-Operative Rehabilitation Resources
These are examples of the type of physiotherapy regimes that you might expect following surgery, although individual hospitals will have their own protocols which may be different depending on some of the technical details of how the surgery is performed.
Many thanks to Celia Wogan (Senior Physiotherapist) and the Bristol Knee Group for sharing their rehabilitation protocols.
Find A Surgeon Near You
The following surgeons have indicated that they have a sub-specialist interest in treating patients with patellofemoral disorders. The BPFS is unable to provide recommendations.