My Knee Hurts

My Knee Hurts

Joseph D. Lamplot, MD

Robert H. Brophy, MD, FAAOS

Dr. Lamplot or an immediate family member serves as a paid consultant to or is an employee of DePuy, a Johnson & Johnson Company and has received research or institutional support from Arthrex, Inc. Dr. Brophy or an immediate family member serves as a board member, owner, officer, or committee member of the American Academy of Orthopaedic Surgeons, the American Orthopaedic Association, and the American Orthopaedic Society for Sports Medicine.


Patellofemoral pain (PFP), a term that encompasses a variety of pathologies involving the patellofemoral joint, is the most common chief complaint associated with the knee and typically presents as anterior knee pain. PFP is not a diagnosis in itself, because it may
result from a variety of etiologies. Atraumatic etiologies for PFP include lateral patellar compression syndrome, chondral softening (chondromalacia patella), and patellofemoral arthritis. Traumatic etiologies include patellar instability (subluxation or dislocation), fracture, patellar or quadriceps tendinitis, and cartilage injuries of the patella or trochlea. A thorough history and physical examination is essential to determine the underlying etiology of PFP. Although an initial course of nonsurgical management is warranted in most cases of PFP, determining the cause of the patient’s symptoms is essential to formulate an appropriate treatment plan. Advanced imaging studies, typically MRI, can be helpful in making a diagnosis.


  • PFP is the most common knee problem of patients presenting to orthopaedic clinics.

  • Lateral patellar compression syndrome occurs secondary to muscular imbalance (ie, vastus medialis oblique [VMO] weakness) and causes patellar maltracking and/or tilt.

    • Most common etiology of PFP, most often affecting adolescent females

  • Patellofemoral arthritis is another common cause of anterior knee pain, most commonly affecting older patients.

  • Chondromalacia patella (softening of the articular cartilage of the patella) occurs in younger patients and may progress to patellofemoral arthritis.

  • Acute chondral injuries are most common in young patients in the setting of patellar dislocations.

    • Commonly affect the medial facet of the patella and lateral aspect of the trochlea

  • Chronic chondral lesions most frequently occur secondary to overload and are typically found in female patients age 30 to 50 years.

Pertinent Anatomy/Pathoanatomy

  • Relevant bony anatomy: tibial tubercle, femoral trochlea, and patella

  • Patella: Composed of smaller medial facet, larger lateral facet, and odd (distal) facet; only medial and lateral facets covered in articular cartilage

  • Trochlear groove: Located at the anterior aspect of the distal femur; functions as bony constraint underlying patellofemoral stability

    • A shallow trochlear groove seen in the setting of trochlear dysplasia and associated with patellar instability

  • Medial patellofemoral ligament (MPFL): Provides static stability to the patella

    • Originates posterior and proximal to the medial epicondyle at Schottle point (Figure 1)

    • Functions as the primary constraint to lateral patellar translation from 0° to 20° of knee flexion

  • Medial and lateral retinacula: Provide static stability to the patellofemoral joint

  • Dynamic stability to the patellofemoral joint conferred primarily by the VMO, which is a medial restraint to lateral translation

    • Other relevant structures: Patellar tendon and distal quadriceps tendon

  • Blood supply: From the geniculate arteries

Pertinent History/Physical Examination Findings

  • History: Thorough history including any injury or trauma related to the onset of anterior knee pain

    • History of instability (dislocation or subluxation)

    • Radicular or hip symptoms: Rule out the lumbar spine or hip as an etiology

    • Effusion or swelling: May suggest intra-articular pathology such as a chondral injury

    • Crepitus and mechanical symptoms: May suggest chondral pathology or arthritis

    • Exacerbating activities such as squatting, ascending, descending stairs

    • Any previous treatments and surgeries

      • If previous physical therapy: Exercises and modalities, frequency and duration of therapy, and patient’s compliance

  • Physical examination

    • Standing alignment and gait

      • Valgus alignment: Higher risk of patellar instability and lateral facet overload

      • A double leg and single leg squat: may demonstrate dynamic valgus collapse, suggesting VMO and/or gluteal insufficiency

      • The patient should be asked to identify the location of maximal pain, which is particularly helpful in patients with anterior knee pain

        • Focal pain at the proximal pole near the quadriceps tendon insertion or distal pole at the patellar tendon origin may suggest overuse or tendinopathy.

    • Seated examination

      • Active knee extension and flexion with the examiner’s hand over the patella

        • Patellar tracking and crepitus

        • J sign or lateral maltracking of the patella as the knee moves into extension out of the bony restraints of the trochlea

      • Resisted quadriceps strength testing: Compare with contralateral side

    • Supine examination

      • Hip range of motion: Identify any pain with range of motion

      • Femoral anteversion

        • Craig test (prone or supine): Palpate patient’s greater trochanter and passively internally rotate hip until its most prominent aspect is at its most lateral position

      • Passive straight leg raise to assess for radicular symptoms

        • Ask patient to contract the bilateral quadriceps; then compare the muscle bulk

      • Active straight leg raise to identify presence of a lag in extensor mechanism

      • Palpate the proximal, distal, medial, and lateral aspects of the patella

      • Place posteriorly directed pressure on the patella and ask the patient to contract the quadriceps, assessing for pain (patellar compression test)

      • Assess patellar tilt and the correctability of tilt

        • With the knee in full extension, place index finger and thumb around patella and determine if there is lateral tilt. If so, assess whether this can be corrected to neutral tilt within the trochlear groove.

      • Apply lateral-directed force to the medial border of the patella to assess the amount of lateral patellar translation and for patellar apprehension

        • Normal motion: less than two quadrants of patellar translation

      • If patellar instability is present, palpate medial border of the patella and medial epicondyle, assessing for tenderness and injury to the MPFL.

      • Palpate iliotibial band insertion on Gerdy tubercle and its course along the lateral femur; iliotibial band syndrome can cause anterolateral knee pain.

      • Determine Beighton score to assess for generalized ligamentous laxity.

      • Palpate medial and lateral infrapatellar tendon spaces: focal pain can indicate symptomatic fat pad impingement.

      • Synovial bands, or plica, may be located anteromedial, anterolateral, superomedial, or superolateral, and can cause symptomatic mechanical symptoms during knee motion; these areas can sometimes be palpated or may lie deep to muscle.

Relevant Imaging

  • Radiographs

    • Standardized knee radiographs: weight-bearing AP, PA Rosenberg (45°), lateral, and Merchant (or sunrise) axial radiographs

      • Axial view to assess depth of the trochlea, lateral subluxation, and tilt

      • Lateral view to evaluate trochlear morphology using criteria established by Dejour1

        • Also to assess for patella alta or patella baja; most often calculated using the Caton-Deschamps ratio (Figure 2)

      • Axial and lateral views to assess for patellofemoral joint space narrowing

  • Advanced imaging: Consider whether thorough history, physical examination, standardized radiographs fail to confirm a diagnosis.

    • MRI sensitive to the presence of pathology that may be incidental and either noncontributory or minimally contributory to the patient’s symptoms

      • May be obtained in the setting of patellar dislocations to assess for intra-articular loose chondral or osteochondral fragments, to assess the chondral surfaces of the patella and trochlea, and to assess other intra-articular structures, including the condyles and menisci

      • Presence of an effusion often suggests an intra-articular injury; MRI should be considered in this setting because plain radiographs cannot reliably establish a diagnosis

        • Effusion with associated anterior knee pain may occur secondary to chondral injury, osteochondral injury, a loose body, or arthritis; MRI can confirm diagnosis and guide treatment.

    • MRI can be used to calculate patellar indices, including the Caton-Deschamps ratio.

      • Also can be used to calculate the tibial tubercle-trochlear groove (TT-TG) distance, a measure of tibial tubercle lateralization that is associated with recurrent patellar instability2

        • TT-TG distance has been shown to be underestimated when measured on MRI compared with CT

    • CT may be considered to assess femoral anteversion (hip to knee CT), because excessive femoral anteversion can contribute to patellar instability.

      • Can be used in a similar manner as MRI to determine the TT-TG distance (Figure 3)

Nonsurgical Measures

  • Initial treatment for most causes of anterior knee pain and should be tailored to the specific diagnosis

  • NSAIDs may help with pain relief, but the most common causes of PFP are not inflammatory.

  • Physical therapy with a focus on VMO, hip, and core strengthening as well as improving squat mechanics

    • A home program should be performed daily.

  • A patellar cutout brace helpful in the setting of patellar maltracking

    • Compression sleeves without a patellar cutout may exacerbate symptoms; generally avoid in this setting.

  • Patellar taping: to improve patellar tilt or subluxation

Surgical Intervention

  • Indications depend on specific cause

  • Patients with loose chondral or osteochondral fragments, which may occur in the setting of a patellar dislocation: knee arthroscopy generally indicated, as the loose fragment(s) may damage healthy surrounding articular cartilage surfaces.

    • If osteochondral fragment is sufficiently large with enough attached bone to potentially heal, fixation may be attempted with a headless compression screw.

  • Skeletally immature patients: Fixation of chondral-only fragments3 or removal of fragments

    • Cartilage restoration procedure depends on age and activity level of patient and location of the lesion(s).

  • In the absence of a loose body, surgical intervention for PFP should occur only after a prolonged course of appropriate physical therapy with patient compliance.

MPFL Reconstruction

  • Indications

    • Commonly performed in the setting of recurrent patellar instability with an incompetent (stretched or torn) MPFL

    • First-time patellar dislocation: If no loose bodies, patients can be treated nonsurgically, with a progressive return to activities over 6 to 12 weeks.

      • Increasing data suggest MPFL reconstruction can be considered in patients with first-time patellar dislocation with multiple risk factors for recurrence—skeletally immaturity, trochlear dysplasia, patella alta.4

    • Recurrent patellar instability: Associated with patellar apprehension, tenderness to palpation along the course of the MPFL
      (including on either the medial epicondyle or medial patellar facet), and increased lateral patellar translation

      • Effusion, particularly in the setting of a chondral or osteochondral injury

      • J sign on active knee extension

        • When actively extending the knee from a flexed position, the patella will move laterally as it exits the trochlear groove

      • Increased lateral patellar tilt: Examiner should determine whether correctible to neutral.

        • If lateral retinaculum is tight and tilt cannot be corrected, arthroscopic lateral retinacular release may be performed; rarely indicated in isolation

      • Axial radiographs may demonstrate a bony MPFL avulsion off the medial facet of the patella or the medial epicondyle; rarely represent intra-articular loose bodies

      • MRI may demonstrate midsubstance tear of the MPFL (most common) or a tear off its femoral or patellar insertion.

    • Chronic patellar instability: Tear may not be identified, but previously injured scar tissue may appear wavy or redundant.

      • Chondral surfaces should be evaluated preoperatively.

        • Most common locations of chondral injuries: Medial patella facet and lateral aspect of trochlea

  • Authors’ preferred technique

    • With patient under anesthesia, amount of patellar translation and end point assessed and compared with contralateral side

      • If patella not fully correctible to neutral, a lateral release may be considered

    • Incision: Along the medial border of the patella from the proximal pole to approximately the midpoint of the patella

    • Dissection is carried down through layer 1 (sartorial fascia) and layer 2, which contains the native MPFL, exposing the joint capsule.

    • Blunt dissection is performed between layers 2 and 3 from the medial border of the patella toward the medial epicondyle for later graft passage

    • The capsule can be carefully incised to demonstrate the patellar articular cartilage.

    • Two suture anchors are inserted as close to the cartilage as possible without violating, with the first near the proximal pole of the patella and the second just proximal to the midpoint.

      • Care must be taken to avoid penetrating the articular cartilage but also not to direct too far anteriorly so as to violate the anterior cortex of the patella.

    • Because there have been no differences shown in outcomes following allograft or autograft tissue, either a semitendinosus allograft or autograft can be used.

      • The center of the graft is marked and placed midway between the two suture anchors.

      • The sutures from each of the anchors are then tied over the graft, thereby securing the graft to the patella.

    • A small incision is made over the medial epicondyle.

    • Dissection is carried down to the medial epicondyle, taking care to protect the saphenous neurovascular bundle.

    • The saddle between the adductor tubercle and medial epicondyle is palpated and radiographically represented as Schottle point.

    • A guide pin is placed at this location under fluoroscopic guidance, directed proximally and anteriorly.

      • The graft can be shuttled through to the medial incision using the previously established interval.

      • Isometry can be tested using the guide pin and passing sutures placed into the graft.

      • Once isometry is confirmed, the guide pin can be overdrilled in preparation for an interference screw.

      • The guide pin is then pulled through along with the passing sutures placed into the graft.

    • The knee is placed at approximately 30° of flexion.

      • The patella should be held reduced in the trochlea and sufficient tension held on the sutures to keep it centered within the trochlea but not overtensioned.

    • The interference screw is then inserted.

  • Postoperative care

    • Weight bearing as tolerated with a hinged knee brace locked in full extension

      • Brace unlocked at postoperative week 6

    • Physical therapy begins within the first 2 to 4 weeks.

    • Return to sport: No sooner than 5 to 6 months after surgery

Tibial Tubercle Osteotomy

  • Indications

    • Performed for chondral surface overload or in setting of recurrent patellar instability with an increased TT-TG distance

    • In setting of recurrent patellar instability, MPFL reconstruction frequently performed concomitantly with tibial tubercle osteotomy

  • Approaches and techniques

    • The most common tibial tubercle osteotomy: Anteromedialization originally described by Fulkerson5 replaces:

      • Elmslie-Trillat, or purely medializing, tibial tubercle osteotomy: Historically used to medialize the tibial tubercle in the setting of tubercle lateralization and recurrent patellar instability

      • Maquet, or purely anteriorizing osteotomy: Historically used to anteriorize the tibial tubercle in the setting of patellar overload to decrease forces across the patellofemoral joint and offload areas of chondrosis

    • Shallow anteromedialization: Osteotomy made at an angle closer to the coronal plane than the sagittal plane; performed to medialize the tibial tubercle to a greater extent than it is anteriorized

      • Most commonly used in the setting of recurrent patellar instability with an increased TT-TG distance

    • Steep anteromedialization: Osteotomy made at an angle closer to the sagittal plane than the coronal plane; performed to anteriorize the tibial tubercle to a greater extent than it is medialized

      • Most commonly used in the setting of patellar chondrosis affecting the distal and lateral aspect of the patella

    • Equipment: Commercially available cutting guide or free-hand using Kirschner wires, osteotomes

    • Keep the proximal extent of the osteotomy at least 1 cm distal to the knee joint to prevent violating the articular cartilage.

    • Protect the patellar tendon at all times.

    • Unless distalization of the tubercle is planned, as in the setting of patella alta, the distalmost aspect of the osteotomized
      tibial tubercle shingle may be left intact to minimize the risk of nonunion.

    • Drill holes for the screws should be made in the anterior aspect of the tubercle before performing the osteotomy cut.

    • Once osteotomy is performed, the tubercle can be moved anteromedially by the templated distance.

    • A Kirschner wire may be placed away from the planned location of screws to maintain the planned reduction

      • 4.5-mm cortical screws may then be placed in lag fashion (Figure 4).

      • A washer may be used on the proximal screw because of poor metaphyseal bone quality in that location.

  • Postoperative care

    • Toe-touch weight bearing for the first 6 weeks postoperatively

    • Immediate passive range of motion from 0° to 90°

    • Straight leg raises and quadriceps sets to prevent quadriceps inhibition

    • Active and active-assisted knee extension not permitted until 6 weeks after surgery

    • Return to sport: No earlier than approximately 6 months postoperatively following a criteria-based return to sport battery of testing

Cartilage Restoration

  • Indications

    • Considered in the setting of high-grade (grade 3 or 4) symptomatic chondral lesions

    • Common presenting signs and symptoms: Recurrent effusions, mechanical symptoms such as catching, pain when the patellofemoral joint is loaded, such as with deep squatting or stair climbing

    • Débridement alone, or chondroplasty, may be considered in older patients (at least age 50 years) without patellofemoral osteoarthritis, in whom the results of cartilage restoration surgery are less predictable and as a staged procedure if autologous cell-based surgery, such as
      matrix-induced autologous chondrocyte implantation (MACI) is planned.

      • MACI requires a biopsy and for the harvested cells to be expanded ex vivo before implantation.

      • Chondroplasty alone may provide sufficient relief of symptoms in these patients, and the second-stage procedure is not necessary.

    • Single-stage cell-based treatments also exist, most commonly in the form of particulated juvenile chondrocytes.

      • These are commercially available but often require a special order and must be used within a certain time period before expiration.

    • Cell-based cartilage restoration techniques can be used only when there are no cystic changes or intralesional osteophytes within the subchondral bone.

      • Subchondral marrow edema alone without the aforementioned degenerative changes is not a contraindication for cell-based strategies.

    • Osteochondral autograft transplantation (OAT) and osteochondral allograft (OCA) are options for symptomatic chondral or osteochondral lesions of the patellofemoral joint.7

      • OAT: For lesions less than 1.5 to 2 cm2, depending on the size of the patient’s knee

      • OCA: For larger lesions but may take longer to incorporate than autograft tissue

  • Approaches and techniques

    • Typically performed via a small medial parapatellar arthrotomy; allows eversion of the patella and access to the entire patella and trochlea

      • Violate as little of the extensor mechanism as necessary to evert the patella and access the pathology.

      • Excise the retropatellar fat pad to help facilitate patellar eversion.

    • Cell-based technique (MACI or juvenile particulated chondrocytes)6

      • Débride lesion to a stable rim of healthy cartilage.

      • Use no. 15 blade and curets (ringed or conventional), taking care to remove the calcified cartilage layer but avoid violating the subchondral bone.

      • The lesion can then be sized before implanting the cell suspension.

      • A thin layer of fibrin glue is typically placed at the base of the lesion before inserting the cells, and then above the cells to seal them in.

      • No irrigation is used after the cells are placed within the lesion.

    • Osteochondral autograft transplantation

      • Autograft plugs up to 1 cm2 harvested from the intercondylar notch or from the periphery of the trochlea, most commonly the superolateral aspect of the trochlea

      • The recipient site is prepared in a similar fashion as the donor plugs are harvested.

        • The injured cartilage and subchondral bone are removed with a core harvester, typically to a depth of 1 cm.

        • When performing OAT on the patella, a guide pin and reamer are recommended rather than a manual harvester, because the subchondral bone is often harder than femoral and trochlear subchondral bone.

      • The depth of the recipient site is confirmed, and the donor plugs are carefully impacted, typically using a delivery tube, to fill the lesion.

        • It is important that the plugs are flush with the surrounding healthy articular cartilage and not proud, as this will predispose to shearing of the donor plugs and graft failure.

    • Osteochondral allograft

      • Although allograft plugs are most commonly taken from a donor femoral condyle, a bulk trochlea or patella may also be used but can be difficult to procure.

        • Authors’ preference: Use circular allograft plugs, which can be sized up to 18 mm2 each and overlap each other

      • Measure chondral lesion, or recipient site, to determine how many and what size plugs are needed to reconstruct the defect.

      • A guide pin is then placed through a sizer, and the recipient site prepared for implantation of a donor plug.

        • Reaming is typically performed no deeper than 8 mm

      • The dimensions of the recipient site are measured, and a donor plug of those same dimensions is harvested from the OCA.

      • The plug is then impacted to fill the recipient site, and the process repeated if additional plugs are needed (Figure 5).

      • Although a press fit is typically used, chondral darts or headless compression screws may be considered as supplemental fixation.

  • Postoperative care

    • Rehabilitation protocols vary.

    • Typically, the knee remains locked in full extension when ambulating with the assistance of crutches for at least the first 6 weeks postoperatively.

    • If early weight bearing allowed, should be with a brace locked in full extension to prevent graft shearing

    • Early motion and quadriceps contractions, including straight leg raises and quad sets, encouraged immediately

    • Return to sport: Typically no sooner than 5 to 6 months after surgery when the athlete passes a criteria-based return to sport battery of testing


Meniscus tears are among the most common pathologies encountered by orthopaedic surgeons. Meniscus tears can be acute/traumatic, most often occurring from a twisting or pivoting injury, or degenerative, although the distinction is not always clear. They can occur in isolation or combined with a knee ligament injury, most frequently an anterior cruciate ligament (ACL) tear. Acute meniscus tears in young athletes, with or without a concomitant ACL injury, more commonly affect the lateral meniscus, whereas degenerative tears most commonly affect the posterior horn of the medial meniscus, although there is considerable overlap. The menisci play a number of important roles in the knee, including decreasing the contact forces between the tibia and femur. Therefore, the menisci should be preserved whenever possible. Because the meniscus has a limited blood supply, primarily in the periphery, not all tears are considered repairable.

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Oct 25, 2023 | Posted by in ORTHOPEDIC | Comments Off on My Knee Hurts

Full access? Get Clinical Tree

Get Clinical Tree app for offline access